m4.5: content-aware [[ linking — autocomplete searches note body

The [[ autocomplete only matched note names, so you could only link a
note you could name. Now it searches note NAME *and* body, so you can
link by recalling any phrase.

- new GET /api/notes/link-search?q= — owner-scoped, non-trashed;
  substring ILIKE on display_title OR body; ranked name-first, then
  name-prefix, then recency; empty q returns recent notes as
  suggestions. Deterministic (no semantic/AI search); the FTS index
  still powers the heavier /search. LIKE wildcards in q are escaped.
- editor [[ autocomplete now calls link-search (debounced 120ms)
  instead of filtering the cached titles index; excludes the note
  itself; inserts the matched note's display name as [[Name]].
- unit tests for the LIKE-escaping + a link-search auth guard.

Second item of M4.5; builds on the display_title work (every note has
a name to link to). Command-palette content search is a natural
follow-on, left out to keep this focused.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/components/NoteEditor.vue

@@ -2,7 +2,7 @@
 import { computed, nextTick, onMounted, ref, watch } from "vue";
 import { api } from "../api/client";
 import { useNotesStore } from "../stores/notes";
-import { useTitlesStore } from "../stores/titles";
+import { useTitlesStore, type TitleEntry } from "../stores/titles";
 import ColorPicker from "./ColorPicker.vue";
 import Icon from "./Icon.vue";
 import LabelPicker from "./LabelPicker.vue";
@@ -93,10 +93,28 @@ const linkQuery = ref("");
 const linkStart = ref(-1); // index of the `[[` that opened the current token
 const linkSelected = ref(0);
 
-const linkMatches = computed(() => {
-  const q = linkQuery.value.trim().toLowerCase();
-  return titles.items.filter((t) => t.title && t.title.toLowerCase().includes(q)).slice(0, 8);
-});
+// [[ autocomplete searches note NAME *and* body via the server (link-search), so you
+// can link by recalling any phrase — not just the exact name. Debounced so we don't
+// fire a request on every keystroke.
+const linkMatches = ref<TitleEntry[]>([]);
+let linkTimer: ReturnType<typeof setTimeout> | undefined;
+
+function refreshLinkMatches() {
+  if (linkTimer) clearTimeout(linkTimer);
+  const q = linkQuery.value.trim();
+  linkTimer = setTimeout(async () => {
+    try {
+      const res = await api.get<{ results: TitleEntry[] }>(
+        `/api/notes/link-search?q=${encodeURIComponent(q)}`,
+      );
+      // Never suggest linking a note to itself.
+      linkMatches.value = res.results.filter((r) => r.id !== props.note.id).slice(0, 8);
+    } catch {
+      linkMatches.value = [];
+    }
+    linkSelected.value = 0;
+  }, 120);
+}
 
 // On every edit, check whether the caret sits inside an unclosed `[[…` token
 // and, if so, open the suggestion menu with the partial title as the query.
@@ -119,6 +137,7 @@ function onBodyInput() {
   linkStart.value = open;
   linkSelected.value = 0;
   linkMenu.value = true;
+  refreshLinkMatches();
 }
 
 function insertLink(title: string) {