M7: unify compose + edit into one NoteEditor (DRY)

The 'Take a note' composer (QuickAdd) and the note editor were two components with duplicated field logic and unequal capabilities — composing lacked [[ links, labels, images, reminders. Merge them into a single NoteEditor with two frames: inline on the board (compose), modal on a card (edit). Same fields, styling, [[ autocomplete and toolbar in both (task 1920).

Compose is now a draft that persists on first real action: on commit-with-content, or on the first label/image/reminder/checklist use (ensureDraft) — so no empty-note litter. Rich controls light up once there's content; note-lifecycle actions (pin/archive/trash, links/backlinks) stay in the modal. notes.create() now returns the created note (for the draft id). QuickAdd.vue deleted; BoardView renders <NoteEditor inline>.

Pure frontend — no backend/DB/migration. Sets up the editor<->card morph (task 1914).

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

frontend/src/stores/notes.ts

@@ -104,8 +104,10 @@ export const useNotesStore = defineStore("notes", () => {
     color: NoteColor;
     kind?: NoteKind;
     items?: string[];
-  }): Promise<void> {
-    reconcile(await api.post<Note>("/api/notes", input));
+  }): Promise<Note> {
+    const note = await api.post<Note>("/api/notes", input);
+    reconcile(note);
+    return note;
   }
 
   async function mutate(