fix: include tags in sync pull response and update API spec

- GET /api/sync now attaches tags to notes (matching GET /api/notes
  and GET /api/search behavior)
- Add trashedAt field to Note schema in OpenAPI spec
- Add optional id field to NoteInput schema
- Add 400 error response for POST /api/sync
- Add response schema for GET attachments list
- Regenerate API.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/routes/api/sync/+server.ts

@@ -1,6 +1,7 @@
 import { json } from '@sveltejs/kit';
 import type { RequestHandler } from './$types.js';
 import { processSyncPush, getChangesSince } from '$lib/sync/server.js';
+import { fetchTagsForNotes } from '$lib/server/tags.js';
 
 export const POST: RequestHandler = async ({ request }) => {
 	const { changes } = await request.json();
@@ -16,5 +17,12 @@ export const POST: RequestHandler = async ({ request }) => {
 export const GET: RequestHandler = async ({ url }) => {
 	const since = parseInt(url.searchParams.get('since') || '0', 10);
 	const changes = await getChangesSince(since);
-	return json(changes);
+
+	const tagMap = fetchTagsForNotes(changes.map((n) => n.id));
+	const changesWithTags = changes.map((note) => ({
+		...note,
+		tags: tagMap.get(note.id) ?? []
+	}));
+
+	return json(changesWithTags);
 };