Fix Android IME typing: editor clobbered its own autosave echo

The $: block applying note changes to CodeMirror listed the autosave
bookkeeping vars (saveTimer, lastKnown) as dependencies, so the 400 ms
autosave re-ran it before App delivered the updated note prop. That stale
run misread the save echo as an external sync change and replaced the
whole doc mid-typing: on Android this aborted every IME composition and
threw the cursor to the top of the note.

Apply note/query via $: fn(prop) so the statements re-run only when the
prop itself changes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/ui/Editor.svelte

@@ -106,39 +106,52 @@
 
   // Swap document when a different note is opened; apply external (sync) changes
   // without clobbering in-flight typing.
-  $: if (view && note) {
-    if (note.id !== currentId) {
+  function applyNote(n: Note) {
+    if (!view || !n) return;
+    if (n.id !== currentId) {
       if (saveTimer) {
         clearTimeout(saveTimer);
         saveTimer = null;
         flushSave(currentId, view.state.doc.toString());
       }
-      currentId = note.id;
-      lastKnown = note.content;
-      view.setState(makeState(note.content));
-    } else if (note.content !== lastKnown) {
+      currentId = n.id;
+      lastKnown = n.content;
+      view.setState(makeState(n.content));
+    } else if (n.content !== lastKnown) {
       // Store changed underneath us (sync pull / conflict replacement) — not an
       // echo of our own autosave. Replace the doc.
-      lastKnown = note.content;
+      lastKnown = n.content;
       if (saveTimer) {
         clearTimeout(saveTimer);
         saveTimer = null;
       }
-      if (note.content !== view.state.doc.toString()) {
-        view.dispatch({ changes: { from: 0, to: view.state.doc.length, insert: note.content } });
+      if (n.content !== view.state.doc.toString()) {
+        view.dispatch({ changes: { from: 0, to: view.state.doc.length, insert: n.content } });
       }
     }
   }
 
   let lastQuery = '';
-  $: if (view && query !== lastQuery) {
-    lastQuery = query;
-    view.dispatch({ effects: searchMark.reconfigure(searchExtension(query)) });
+  function applyQuery(q: string) {
+    if (!view || q === lastQuery) return;
+    lastQuery = q;
+    view.dispatch({ effects: searchMark.reconfigure(searchExtension(q)) });
   }
 
+  // Deliberately `$: fn(prop)` instead of inlining the logic in a reactive
+  // block: these must re-run ONLY when the prop itself changes. Svelte tracks
+  // every variable a `$:` statement mentions (including writes like
+  // `saveTimer = null` deep in the autosave path), and a re-run triggered by
+  // our own bookkeeping sees a stale `note`, misreads the autosave echo as an
+  // external sync change, and replaces the doc mid-typing — which on Android
+  // aborts IME composition and throws the cursor to the top of the note.
+  $: applyNote(note);
+  $: applyQuery(query);
+
   onMount(() => {
     currentId = note.id;
     lastKnown = note.content;
+    lastQuery = query; // makeState below bakes in the current query
     view = new EditorView({ state: makeState(note.content), parent: host });
   });