web: task lines render as checkboxes where they sit in the note

M304 step 5. The server already returns a derived `items` array, so the web kept
working across the last two commits — but it was rendering every list TWICE: once
as literal `- [ ] milk` bullets inside the body, and again as the separate
NoteChecklist block underneath. This is the commit that makes the body the only
place a checklist appears.

markdown.ts gains a `task` block, matched BEFORE the plain bullet — which would
otherwise swallow the marker and leave the brackets showing, the same ordering
reason `code` is matched before emphasis in INLINE_RE. Each item carries its
ordinal across the WHOLE document, because that is what an item's id means
everywhere else now; counting per block would have made the second list's
checkboxes toggle the first list's items.

The card's preview clamp is why that ordinal is safe there: it only ever drops
lines from the end, so a visible item's index is the same whether or not the body
was truncated.

MarkdownText emits a toggle rather than reaching for the store. Ticking a box
rewrites a line of someone's note, and a renderer used in several places should not
be the thing deciding that is allowed — the card passes `toggleable` and wires it,
a read-only render does not and the boxes are inert. Not wrapped in a <label>
either: on a card the text is the note's own words and clicking it opens the note,
so only the box toggles.

In the editor, the toolbar button stops revealing a section and inserts `- [ ] ` at
the caret. That makes it the one toolbar action needing no persisted note to hang
anything off — ensureDraft is gone from it, and it works on an empty compose box
the moment it opens. Enter on a task line continues the list, and on an EMPTY one
clears the marker; without that second half a list would be impossible to get out
of. Indent and bullet are carried over rather than normalised, because continuing
someone's `*` list with a `-` is an edit they did not ask for.

NoteChecklist.vue is deleted (rule 22). The store's item methods stay: they are the
repository seam the REST routes and Tauri commands both implement, not the old path.

CI cannot check any of this beyond types — there are no frontend tests, only
vue-tsc. It wants a real browser pass.

frontend/src/components/MarkdownText.vue

@@ -3,7 +3,12 @@ import { computed } from "vue";
 import { parseMarkdown } from "../notes/markdown";
 import MarkdownInline from "./MarkdownInline.vue";
 
-const props = defineProps<{ text: string }>();
+const props = defineProps<{ text: string; toggleable?: boolean }>();
+// Ticking a box rewrites a line of the note's body, which is a thing only the owner
+// of that note can do — so this renders the checkbox and hands the intent up rather
+// than reaching for the store itself. The card wires it; a read-only render does not
+// pass `toggleable` and the boxes are inert.
+const emit = defineEmits<{ toggle: [index: number, checked: boolean] }>();
 const blocks = computed(() => parseMarkdown(props.text));
 </script>
 
@@ -19,6 +24,28 @@ const blocks = computed(() => parseMarkdown(props.text));
       >
         <MarkdownInline :tokens="b.inline ?? []" />
       </blockquote>
+      <div v-else-if="b.type === 'task'" class="flex flex-col gap-1">
+        <div v-for="(it, j) in b.items ?? []" :key="j" class="flex items-start gap-2">
+          <!-- Not wrapped in a <label>: on a card the text is the note's own words and
+               clicking it opens the note, so only the box itself toggles. `.stop` for
+               the same reason — the card is a click target underneath. -->
+          <input
+            type="checkbox"
+            class="mt-0.5 h-4 w-4 shrink-0 accent-brand"
+            :checked="b.tasks?.[j]?.checked ?? false"
+            :disabled="!toggleable"
+            :aria-label="toggleable ? 'Toggle item' : undefined"
+            @click.stop
+            @change="emit('toggle', b.tasks?.[j]?.index ?? 0, ($event.target as HTMLInputElement).checked)"
+          />
+          <span
+            class="min-w-0 flex-1"
+            :class="b.tasks?.[j]?.checked ? 'text-neutral-400 line-through' : ''"
+          >
+            <MarkdownInline :tokens="it" />
+          </span>
+        </div>
+      </div>
       <ul v-else-if="b.type === 'ul'" class="list-disc space-y-0.5 pl-5">
         <li v-for="(it, j) in b.items ?? []" :key="j"><MarkdownInline :tokens="it" /></li>
       </ul>

frontend/src/components/NoteCard.vue

@@ -13,7 +13,6 @@ import type { Note } from "../stores/notes";
 import Icon from "./Icon.vue";
 import LinkPreview from "./LinkPreview.vue";
 import MarkdownText from "./MarkdownText.vue";
-import NoteChecklist from "./NoteChecklist.vue";
 import {
   cardIdAt,
   draggingId,
@@ -94,6 +93,15 @@ const bodyPreview = computed(() => {
   return lines.slice(0, PREVIEW_LINES).join("\n") + "\n…";
 });
 
+/** Tick a box without opening the note — the common gesture on a board.
+ *
+ *  The index is the item's ordinal in the WHOLE body, which survives the preview
+ *  clamp above because that only ever drops lines from the end. `updateItem` takes
+ *  it as the item id, which is exactly what an id is now (M304). */
+function toggleTask(index: number, checked: boolean) {
+  void notes.updateItem(props.note.id, String(index), { checked });
+}
+
 const root = ref<HTMLElement | null>(null);
 
 // --- Drag-to-reorder. Pointer Events, gated behind an explicit grip handle so a
@@ -263,7 +271,7 @@ onBeforeUnmount(() => document.removeEventListener("mousedown", onDocMousedown))
            blank and the link is never unreachable. -->
       <LinkPreview v-if="loneUrlPreview" :preview="loneUrlPreview" />
       <div v-else-if="note.body" class="text-sm text-neutral-700 dark:text-neutral-300">
-        <MarkdownText :text="bodyPreview" />
+        <MarkdownText :text="bodyPreview" toggleable @toggle="toggleTask" />
       </div>
       <p
         v-if="!note.body && !note.items.length && !note.attachments.length"
@@ -279,13 +287,10 @@ onBeforeUnmount(() => document.removeEventListener("mousedown", onDocMousedown))
       <LinkPreview v-for="p in note.previews" :key="p.id" :preview="p" compact />
     </div>
 
-    <NoteChecklist
-      v-if="note.items.length"
-      :class="note.body ? 'mt-2' : ''"
-      :note-id="note.id"
-      :items="note.items"
-      @click="emit('open', note)"
-    />
+    <!-- No separate checklist block any more. A checklist is lines of the body (M304),
+         so MarkdownText above draws it in place — which is what lets a list sit between
+         two paragraphs instead of always after them. Rendering both would have shown
+         every list twice. -->
 
     <div v-if="note.labels.length" class="mt-2 flex flex-wrap gap-1">
       <span

frontend/src/components/NoteChecklist.vue

@@ -1,75 +0,0 @@
-<script setup lang="ts">
-import { ref } from "vue";
-import { useNotesStore, type ChecklistItem } from "../stores/notes";
-
-const props = defineProps<{ noteId: string; items: ChecklistItem[]; editable?: boolean }>();
-const notes = useNotesStore();
-const newItem = ref("");
-
-async function addItem() {
-  const text = newItem.value.trim();
-  if (!text) return;
-  await notes.addItem(props.noteId, text);
-  newItem.value = "";
-}
-
-function toggle(item: ChecklistItem) {
-  void notes.updateItem(props.noteId, item.id, { checked: !item.checked });
-}
-
-function editText(item: ChecklistItem, value: string) {
-  if (value !== item.text) void notes.updateItem(props.noteId, item.id, { text: value });
-}
-
-function remove(item: ChecklistItem) {
-  void notes.deleteItem(props.noteId, item.id);
-}
-</script>
-
-<template>
-  <div class="flex flex-col gap-1">
-    <div v-for="item in items" :key="item.id" class="group/item flex items-center gap-2">
-      <input
-        type="checkbox"
-        class="h-4 w-4 shrink-0 accent-brand"
-        :checked="item.checked"
-        @change="toggle(item)"
-        @click.stop
-      />
-      <input
-        v-if="editable"
-        :value="item.text"
-        class="min-w-0 flex-1 bg-transparent text-sm outline-none"
-        :class="item.checked ? 'text-neutral-400 line-through' : ''"
-        @change="editText(item, ($event.target as HTMLInputElement).value)"
-      />
-      <span
-        v-else
-        class="min-w-0 flex-1 truncate text-sm"
-        :class="item.checked ? 'text-neutral-400 line-through' : 'text-neutral-700 dark:text-neutral-300'"
-        >{{ item.text }}</span
-      >
-      <button
-        v-if="editable"
-        type="button"
-        class="hover-reveal text-neutral-300 opacity-0 hover:text-neutral-600 group-hover/item:opacity-100 dark:hover:text-neutral-200"
-        aria-label="Delete item"
-        @click="remove(item)"
-      >
-        ×
-      </button>
-    </div>
-
-    <form v-if="editable" class="mt-1 flex items-center gap-2" @submit.prevent="addItem">
-      <span class="h-4 w-4 shrink-0" />
-      <input
-        v-model="newItem"
-        type="text"
-        placeholder="+ List item"
-        class="min-w-0 flex-1 bg-transparent text-sm outline-none placeholder:text-neutral-400"
-      />
-    </form>
-
-    <p v-if="!editable && items.length === 0" class="text-sm italic text-neutral-400">Empty checklist</p>
-  </div>
-</template>

frontend/src/components/NoteEditor.vue

@@ -5,7 +5,6 @@ import ColorPicker from "./ColorPicker.vue";
 import Icon from "./Icon.vue";
 import LabelPicker from "./LabelPicker.vue";
 import LinkPreview from "./LinkPreview.vue";
-import NoteChecklist from "./NoteChecklist.vue";
 import { fromLocalInput, toLocalInput } from "../notes/datetime";
 import { takeMorphOrigin } from "../composables/useEditorMorph";
 import { prefersReducedMotion } from "../composables/useReducedMotion";
@@ -31,7 +30,6 @@ const labelList = ref<NoteLabel[]>(props.note ? [...props.note.labels] : []);
 // Whether this editor is showing the checklist. A note HAS a checklist (M13 step 2)
 // rather than BEING one, so this is a view flag, not a property of the note: it turns
 // on when the note already carries items, and when someone asks for one.
-const checklistOpen = ref(false);
 const saving = ref(false);
 const root = ref<HTMLElement | null>(null);
 const bodyInput = ref<HTMLTextAreaElement | null>(null);
@@ -75,15 +73,6 @@ const liveNote = computed<Note>(() =>
     ? (notes.items.find((n) => n.id === noteId.value) ?? props.note ?? draftNote.value)
     : draftNote.value,
 );
-// The checklist renders once the note has items, or once someone has asked for one.
-// It sits BELOW the body rather than instead of it — a note can carry both, which is
-// the whole point of the merge.
-//
-// Items need a persisted note to hang off, so this is a rich action like attaching a
-// file: in compose it waits for the draft to be saved.
-const showChecklist = computed(
-  () => !isCreate.value && (liveNote.value.items.length > 0 || checklistOpen.value),
-);
 const bodyPlaceholder = "Take a note…";
 
 // Keep local state in sync when the edited note changes (modal reused for another note).
@@ -145,7 +134,6 @@ function resetCompose(): void {
   body.value = "";
   color.value = "default";
   labelList.value = [];
-  checklistOpen.value = false;
   baseline.value = { body: "", color: "default" };
   uploadError.value = "";
 }
@@ -233,6 +221,10 @@ onMounted(async () => {
   if (el) el.selectionStart = el.selectionEnd = el.value.length;
 });
 
+// The same grammar as notes/markdown.ts, narrowed to one line so the pieces can be
+// put back. See that file for why three implementations of it exist.
+const TASK_LINE_RE = /^(\s*)([-*]) +\[([ xX])\](?: +(.*))?$/;
+
 function onBodyKeydown(e: KeyboardEvent) {
   // Compose: Shift+Enter saves the note and starts a fresh one (rapid capture).
   if (isCreate.value && e.key === "Enter" && e.shiftKey) {
@@ -240,6 +232,36 @@ function onBodyKeydown(e: KeyboardEvent) {
     void commitAndContinue();
     return;
   }
+
+  // Enter on a task line starts the next one; on an EMPTY task line it clears the
+  // marker instead. Both halves are needed — without the second, a list would be
+  // impossible to get out of without deleting characters by hand.
+  if (e.key !== "Enter" || e.shiftKey || e.ctrlKey || e.metaKey || e.altKey) return;
+  const el = e.target as HTMLTextAreaElement;
+  const start = el.selectionStart ?? 0;
+  // A selection means Enter is replacing something; let the browser do it.
+  if (start !== el.selectionEnd) return;
+  const before = body.value.slice(0, start);
+  const rest = body.value.slice(start);
+  // Only at the END of a line. Mid-line, Enter splits the line, which is what anyone
+  // pressing it there meant.
+  if (rest !== "" && !rest.startsWith("\n")) return;
+  const lineStart = before.lastIndexOf("\n") + 1;
+  const match = TASK_LINE_RE.exec(before.slice(lineStart));
+  if (!match) return;
+
+  e.preventDefault();
+  if (!(match[4] ?? "").trim()) {
+    body.value = body.value.slice(0, lineStart) + rest;
+    void nextTick(() => el.setSelectionRange(lineStart, lineStart));
+    return;
+  }
+  // The bullet and indent are carried over, not normalised: continuing someone's
+  // `*` list with a `-` would be an edit they did not ask for.
+  const marker = `${match[1]}${match[2]} [ ] `;
+  body.value = `${before}\n${marker}${rest}`;
+  const caret = start + 1 + marker.length;
+  void nextTick(() => el.setSelectionRange(caret, caret));
 }
 
 // ---- reminder ----
@@ -285,14 +307,27 @@ function labelChip(c: string): string {
 
 // ---- add a checklist ----
 //
-// Not a conversion any more. Nothing is moved, nothing is swapped: the note keeps its
-// body and gains a place to put items. Persists the draft first for the same reason
-// attaching a file does — an item needs a note to belong to.
+// Inserts `- [ ] ` at the caret. That is the whole action now: a checklist is lines of
+// the body (M304), so unlike every other toolbar button this one needs NO persisted
+// note to hang anything off — `ensureDraft` is gone from it, and it works on an empty
+// compose box the moment it opens.
 async function addChecklist() {
-  if (checklistOpen.value) return;
-  const id = await ensureDraft();
-  if (!id) return;
-  checklistOpen.value = true;
+  const el = bodyInput.value;
+  const marker = "- [ ] ";
+  if (!el) {
+    body.value = body.value ? `${body.value.replace(/\n+$/, "")}\n${marker}` : marker;
+    return;
+  }
+  const start = el.selectionStart ?? body.value.length;
+  const before = body.value.slice(0, start);
+  // Start a new line unless the caret already sits at the beginning of one — a marker
+  // in the middle of a sentence is not a list item, it is a typo.
+  const prefix = before === "" || before.endsWith("\n") ? "" : "\n";
+  body.value = `${before}${prefix}${marker}${body.value.slice(start)}`;
+  const caret = start + prefix.length + marker.length;
+  await nextTick();
+  el.focus();
+  el.setSelectionRange(caret, caret);
 }
 
 // ---- attachments ----
@@ -482,14 +517,8 @@ function revPreview(rev: NoteRevision): string {
           class="w-full resize-none bg-transparent text-sm leading-relaxed outline-none placeholder:text-neutral-400"
           @keydown="onBodyKeydown"
         />
-        <!-- Below the body, not instead of it. -->
-        <NoteChecklist
-          v-if="showChecklist"
-          class="py-1"
-          :note-id="liveNote.id"
-          :items="liveNote.items"
-          editable
-        />
+        <!-- No checklist component. The items are lines of the textarea above, which
+             is what lets a list sit between two paragraphs (M304). -->
 
         <div v-if="labelList.length" class="flex flex-wrap gap-1.5 pt-1">
           <span
@@ -598,7 +627,7 @@ function revPreview(rev: NoteRevision): string {
           </button>
           <input ref="fileInput" type="file" class="hidden" @change="onFileChange" />
           <button
-            v-if="richEnabled && !liveNote.trashed && !showChecklist"
+            v-if="!liveNote.trashed"
             type="button"
             class="icon-btn"
             title="Add a checklist"

frontend/src/notes/markdown.ts

@@ -13,10 +13,22 @@ export interface InlineToken {
 
 // Flat (non-discriminated) shape on purpose — keeps template type-checking simple.
 export interface Block {
-  type: "p" | "h1" | "h2" | "h3" | "quote" | "ul" | "ol" | "pre";
+  type: "p" | "h1" | "h2" | "h3" | "quote" | "ul" | "ol" | "pre" | "task";
   inline?: InlineToken[];
   items?: InlineToken[][];
   value?: string;
+  /** `task` only: one entry per `items` entry, parallel by position. */
+  tasks?: TaskMeta[];
+}
+
+export interface TaskMeta {
+  /** This item's ordinal among ALL task lines in the body, in document order.
+   *  That is the id the server and the native clients address an item by, so a
+   *  checkbox can be toggled straight from it. Counted across blocks, not within
+   *  one, and unaffected by the card truncating the body — the card only ever
+   *  drops lines from the END. */
+  index: number;
+  checked: boolean;
 }
 
 // Order matters: code is matched before emphasis so its contents aren't re-parsed;
@@ -44,11 +56,24 @@ export function parseInline(text: string): InlineToken[] {
   return tokens;
 }
 
+// A checklist item: the third implementation of one grammar, alongside
+// core/src/local/derive.rs and src/thoughtsync/notes/checklist.py. A difference
+// between any two of them is a checklist that changes shape when it syncs (M304).
+//
+// `-` and `*` only, deliberately, even though the `ul` matcher below also takes `+`.
+// The other two implementations do not take `+`, and one grammar in three places has
+// to be one grammar; a `+ [ ] x` line renders as an ordinary bullet everywhere,
+// which is at least consistent.
+const TASK_RE = /^\s*[-*] +\[([ xX])\](?: +(.*))?$/;
+
 export function parseMarkdown(text: string): Block[] {
   const lines = (text ?? "").split("\n");
   const blocks: Block[] = [];
   let paragraph: string[] = [];
   let i = 0;
+  // Runs across the whole document, not per block, because that is what the item's
+  // id means everywhere else.
+  let taskIndex = 0;
 
   const flushPara = () => {
     if (paragraph.length) {
@@ -96,6 +121,25 @@ export function parseMarkdown(text: string): Block[] {
       continue;
     }
 
+    // Task list, BEFORE the plain bullet below — which would otherwise swallow
+    // `- [ ] x` as an ordinary list item and leave the brackets showing. Same
+    // ordering reason as `code` being matched before emphasis in INLINE_RE.
+    if (TASK_RE.test(line)) {
+      flushPara();
+      const items: InlineToken[][] = [];
+      const tasks: TaskMeta[] = [];
+      while (i < lines.length) {
+        const m = TASK_RE.exec(lines[i]);
+        if (!m) break;
+        items.push(parseInline(m[2] ?? ""));
+        tasks.push({ index: taskIndex, checked: m[1] !== " " });
+        taskIndex++;
+        i++;
+      }
+      blocks.push({ type: "task", items, tasks });
+      continue;
+    }
+
     // Unordered list: -, *, or + then a space.
     if (/^\s*[-*+]\s+/.test(line)) {
       flushPara();