feat(ui): a note's check is editable, dated and sweepable (#3167, milestone 317 step 4)

Rule 27: no UI, no ship. Three surfaces.

THE EDITOR ASKS, but only where the answer can be saved: the fields appear
for a plain note and not for a task or a snippet, matching the service gate
from step 2 so the form never offers a write the save would reject. The
labels are phrased as the QUESTION rather than the field name — "how would
someone check this is still true?" and, underneath, "could this become false
without anyone editing it?". "Verify with" gets filled in on every note; the
question gets filled in on the few that can go stale. `expires_when` appears
only once a check exists, and asks for a state rather than a date in the
placeholder itself.

THE NOTE SHOWS ITS AGE beside the field — "checked 2026-08-28" or "never
checked", italic, and nothing at all when no check exists. No red/amber ramp,
matching RuleSweepPane: a colour scale would restate the sweep's ordering and
force an invented staleness threshold. "Never" is marked because it is
categorically different from a date, not a worse one.

THE SWEEP is a pane in the Knowledge view, not beside the rules sweep —
operator's call, taken over a unified "everything due" surface and over a
second pane under /rules. Notes stay where notes live. The cost, accepted
knowingly: no single screen shows every unconfirmed record. It REPLACES the
feed rather than filtering it, because a facet answers "show me this kind"
and this answers "show me what nobody has confirmed" — a question the type
chips cannot narrow without under-reporting.

Two REST routes for it, since step 3 built only the service and the MCP door.

Along the way: NoteEditorView spelled its write payload out at three call
sites (save, create, auto-save), so every new field had to be added three
times — which is how one of them ends up not carrying it. Now one `payload()`
and one `snapshot()`.

Known and filed, not fixed: NoteSweepPane copies ~12 scoped CSS rules from
RuleSweepPane (#3207). The clean extraction needs prefixed names, because
`.age`, `.row-title`, `.lede` and `.actions` all exist scoped in other
components and an unscoped global would leak into them — which means editing
the shipped rules sweep, blind, inside a step whose acceptance is the
operator looking at a different surface.

frontend/src/components/NoteSweepPane.vue

@@ -0,0 +1,198 @@
+<script setup lang="ts">
+/**
+ * The staleness sweep for NOTES: notes that assert a fact, oldest first.
+ *
+ * Sibling of RuleSweepPane, not a shared component — the two read differently
+ * enough that merging them would mean a prop for every difference (a rule has
+ * a tier and a statement; a note has a project and opens at a route). What
+ * they share is the SHAPE of the judgement, and that is worth copying
+ * deliberately rather than abstracting: the ordering carries urgency, "never"
+ * is categorically different from a date, and a failed check writes nothing.
+ *
+ * Lives in the Knowledge view rather than beside the rules sweep (operator's
+ * call, milestone 317 step 4): notes stay where notes live. The cost, accepted
+ * knowingly, is that there is no single screen showing every record anyone has
+ * left unconfirmed — /rules keeps its own.
+ */
+import { onMounted, ref } from "vue";
+import { apiGet, apiPost } from "@/api/client";
+import { useToastStore } from "@/stores/toast";
+
+interface DueNote {
+  id: number;
+  title: string;
+  project_id: number | null;
+  verify_with: string;
+  expires_when: string;
+  last_verified: string | null;
+  days_since_verified: number | null;
+}
+
+const emit = defineEmits<{ "open-note": [id: number] }>();
+
+const toast = useToastStore();
+const rows = ref<DueNote[]>([]);
+const loading = ref(false);
+const neverOnly = ref(false);
+const busyId = ref<number | null>(null);
+
+async function reload() {
+  loading.value = true;
+  try {
+    const p = new URLSearchParams();
+    if (neverOnly.value) p.set("never_only", "1");
+    const data = await apiGet<{ notes: DueNote[] }>(
+      `/api/notes/due-for-verification?${p}`,
+    );
+    rows.value = data.notes;
+  } catch {
+    toast.show("Could not load the sweep", "error");
+  } finally {
+    loading.value = false;
+  }
+}
+
+async function verify(id: number, stillTrue: boolean) {
+  busyId.value = id;
+  try {
+    await apiPost(`/api/notes/${id}/verify`, { still_true: stillTrue });
+    if (stillTrue) {
+      // It has been confirmed, so it leaves the list — the sweep shows what
+      // still needs looking at, and leaving it in place would invite a second
+      // stamp nobody earned.
+      rows.value = rows.value.filter((r) => r.id !== id);
+      toast.show("Recorded — checked today");
+    } else {
+      // It stays. A failed check writes nothing on purpose: the note is wrong
+      // rather than in a state worth recording, so it keeps its place until
+      // someone corrects, supersedes, or unhooks it.
+      toast.show("Recorded as no longer true — the note keeps its place here");
+    }
+  } catch {
+    toast.show("Could not record that", "error");
+  } finally {
+    busyId.value = null;
+  }
+}
+
+onMounted(reload);
+defineExpose({ reload });
+</script>
+
+<template>
+  <section class="sweep">
+    <header>
+      <h2>Due for verification</h2>
+      <p class="lede">
+        Notes that assert a fact about something outside your control — what a
+        service does, how a tool behaves. Most notes are decisions and never
+        appear here; they have no truth value to go stale.
+      </p>
+    </header>
+
+    <div class="filters">
+      <label class="filter">
+        <input v-model="neverOnly" type="checkbox" @change="reload" />
+        <span>Never checked only</span>
+      </label>
+    </div>
+
+    <p v-if="loading" class="state">Loading…</p>
+
+    <!-- An empty sweep is GOOD NEWS and must not read like a broken page. -->
+    <p v-else-if="!rows.length" class="state empty">
+      Nothing to check.
+      {{ neverOnly
+        ? "Every note that carries a check has been confirmed at least once."
+        : "No note carries a check yet — add one to a note that asserts a fact." }}
+    </p>
+
+    <ol v-else class="rows">
+      <li v-for="n in rows" :key="n.id" class="row">
+        <div class="row-head">
+          <button class="row-title" @click="emit('open-note', n.id)">{{ n.title }}</button>
+          <span class="age" :class="{ unchecked: n.days_since_verified === null }">
+            {{ n.days_since_verified === null
+              ? "never checked"
+              : `${n.days_since_verified}d ago` }}
+          </span>
+        </div>
+
+        <dl class="check">
+          <dt>Check</dt>
+          <dd>{{ n.verify_with }}</dd>
+          <template v-if="n.expires_when">
+            <dt>Ends when</dt>
+            <dd>{{ n.expires_when }}</dd>
+          </template>
+        </dl>
+
+        <div class="actions">
+          <button :disabled="busyId === n.id" @click="verify(n.id, true)">Still true</button>
+          <button :disabled="busyId === n.id" @click="verify(n.id, false)">No longer true</button>
+        </div>
+      </li>
+    </ol>
+
+    <p v-if="rows.length" class="footnote">
+      Record a result only after actually running the check. “No longer true” stores nothing
+      on purpose — the note is wrong rather than in a state worth recording, so it keeps its
+      place here until you correct it, supersede it, or remove its check.
+    </p>
+  </section>
+</template>
+
+<style scoped>
+.sweep { display: flex; flex-direction: column; gap: var(--fs-space-3); }
+h2 { margin: 0; font-size: 1.05rem; }
+.lede {
+  margin: 0.35rem 0 0;
+  max-width: 62ch;
+  font-size: 0.85rem;
+  color: var(--fs-text-secondary);
+  line-height: 1.5;
+}
+
+.filters { display: flex; gap: var(--fs-space-5); align-items: center; flex-wrap: wrap; }
+.filter { display: flex; align-items: center; gap: var(--fs-space-2); font-size: 0.82rem; color: var(--fs-text-secondary); }
+.filter input[type="checkbox"] { accent-color: var(--fs-accent); }
+
+.state { margin: 0; font-size: 0.9rem; color: var(--fs-text-secondary); }
+.state.empty { color: var(--fs-text-tertiary); }
+
+.rows { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: var(--fs-space-3); }
+.row {
+  background: var(--fs-surface-raised);
+  border-radius: var(--fs-radius-md);
+  padding: var(--fs-space-3);
+}
+.row-head { display: flex; align-items: baseline; gap: var(--fs-space-2); flex-wrap: wrap; }
+.row-title {
+  background: none; border: none; padding: 0; cursor: pointer;
+  font-family: Fraunces, serif; font-style: italic; font-size: 1.02rem;
+  color: var(--fs-text-primary); text-align: left;
+}
+.row-title:hover { text-decoration: underline; }
+/* The ORDER carries urgency — the top of this list is the least-confirmed
+   thing in the corpus. No red/amber ramp: it would restate the ordering and
+   force an invented "stale after N days" threshold. "Never" is marked because
+   it is categorically DIFFERENT from a date, not a worse one. */
+.age { margin-left: auto; font-size: 0.78rem; color: var(--fs-text-secondary); font-variant-numeric: tabular-nums; }
+.age.unchecked { font-style: italic; color: var(--fs-text-tertiary); }
+
+.check { display: grid; grid-template-columns: auto 1fr; gap: 0.15rem var(--fs-space-3); margin: var(--fs-space-3) 0 0; }
+.check dt { font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.05em; color: var(--fs-text-tertiary); }
+.check dd { margin: 0; font-size: 0.82rem; color: var(--fs-text-primary); min-width: 0; overflow-wrap: anywhere; }
+
+.actions { display: flex; gap: var(--fs-space-2); margin-top: var(--fs-space-3); }
+.actions button {
+  cursor: pointer; font: inherit; font-size: 0.78rem;
+  background: var(--fs-surface-page); color: var(--fs-text-primary);
+  border: 1px solid var(--fs-border-color); border-radius: var(--fs-radius-md);
+  padding: 0.25rem 0.6rem;
+}
+.actions button:hover:not(:disabled) { background: var(--fs-surface-hover); }
+.actions button:disabled { opacity: var(--fs-disabled-opacity); cursor: default; }
+
+.footnote { margin: 0; max-width: 62ch; font-size: 0.78rem; color: var(--fs-text-tertiary); line-height: 1.45; }
+</style>