Fix Cmd+N creating duplicate notes in dev mode

The Tauri event listeners were registered via async Promise.all, but
cleanup ran before promises resolved (unlisten vars still null). In
React StrictMode this left two active listeners per event, causing
double note creation. Use a cancelled flag so late-resolving disposers
clean up immediately.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ChristianChiarulli

app/src/app.tsx

@@ -215,40 +215,26 @@ function App() {
   });
 
   useEffect(() => {
-    let unlistenCommandPalette: (() => void) | null = null;
-    let unlistenEditorFind: (() => void) | null = null;
-    let unlistenNewNote: (() => void) | null = null;
-    let unlistenNotesSearch: (() => void) | null = null;
-    let unlistenSettings: (() => void) | null = null;
+    let cancelled = false;
+    const disposers: (() => void)[] = [];
 
     void Promise.all([
       listen(TAURI_EVENT_COMMAND_PALETTE, handleCommandPaletteMenuEvent),
       listen(TAURI_EVENT_EDITOR_FIND, handleEditorFindMenuEvent),
       listen(TAURI_EVENT_NEW_NOTE, handleNewNoteMenuEvent),
       listen(TAURI_EVENT_NOTES_SEARCH, handleNotesSearchMenuEvent),
       listen(TAURI_EVENT_SETTINGS, handleSettingsMenuEvent),
-    ]).then(
-      ([
-        disposeCommandPalette,
-        disposeEditorFind,
-        disposeNewNote,
-        disposeNotesSearch,
-        disposeSettings,
-      ]) => {
-        unlistenCommandPalette = disposeCommandPalette;
-        unlistenEditorFind = disposeEditorFind;
-        unlistenNewNote = disposeNewNote;
-        unlistenNotesSearch = disposeNotesSearch;
-        unlistenSettings = disposeSettings;
-      },
-    );
+    ]).then((unlistenFns) => {
+      if (cancelled) {
+        for (const fn of unlistenFns) fn();
+      } else {
+        disposers.push(...unlistenFns);
+      }
+    });
 
     return () => {
-      unlistenCommandPalette?.();
-      unlistenEditorFind?.();
-      unlistenNewNote?.();
-      unlistenNotesSearch?.();
-      unlistenSettings?.();
+      cancelled = true;
+      for (const fn of disposers) fn();
     };
   }, []);