feat(M002): smart playlists — rule engine, editor UI, sidebar integration

Recovered from orphaned worktree commits (complete-milestone failed to merge).

Backend:
- Migration 9: is_smart + smart_rules columns on playlists table
- smartplaylist package: parameterized WHERE clause builder, field whitelist, genre subquery
- playlist.Service: Create/Update/Evaluate/Preview/GetRules smart playlist methods
- 65 tests (49 rule engine + 15 service + 1 migration)

Frontend:
- yj-combobox: reusable typeable dropdown with keyboard nav, ARIA, blur-race fix
- smart-playlist-editor: row-based rule builder with live preview
- smart-playlist-details: evaluate, refresh, play, shuffle, edit rules
- Sidebar: filter icon, Smart badge, create button, routing
- Queue snapshot on play/shuffle

frontend/index.ts

@@ -11,6 +11,8 @@ import '@components/artist-details/artist-details.ts';
 import '@components/genres-view/genres-view.ts';
 import '@components/genre-details/genre-details.ts';
 import '@components/playlist-details/playlist-details.ts';
+import '@components/smart-playlist-details/smart-playlist-details.ts';
+import '@components/smart-playlist-editor/smart-playlist-editor.ts';
 import '@components/search-bar/search-bar.ts';
 import '@components/library-filter/library-filter.ts';
 import '@components/track-details/track-details.ts';
@@ -139,6 +141,19 @@ document.addEventListener('navigate', (e: Event) => {
             currentDetailEl = plEl;
             break;
         }
+        case 'smart-playlist-details': {
+            const { playlistId, playlistName } = detail;
+            const spEl = document.createElement('smart-playlist-details');
+
+            spEl.setAttribute('playlist-id', String(playlistId));
+            spEl.setAttribute('playlist-name', playlistName);
+            if (detail.autoEdit) {
+                spEl.setAttribute('auto-edit', '');
+            }
+            mainContent.appendChild(spEl);
+            currentDetailEl = spEl;
+            break;
+        }
         case 'genre-details': {
             const { genreName } = detail;
             const genreEl = document.createElement('genre-details');