v3 library: song Details drawer + bulk edit — P2 (#703)

* v3 library: song Details drawer + bulk edit — P2

Evolves the per-song editing surface from the legacy modal into a v3
slide-in Details drawer (the filter-drawer idiom, body-appended): catalog
fields (title/artist/album/year, written through the existing atomic
manifest writer) plus the P1 personal layer - your difficulty (1-5),
tags, and notes - with the heart staying the existing favorite system.

- Cards badge the personal layer at rest (difficulty pip + tag count,
  top-right, fading on hover so the action buttons keep that corner);
  un-annotated cards render byte-identical to before.
- Bulk edit from the select-mode batch bar: POST
  /api/songs/user-meta/batch applies additive tag add/remove and a
  leave/set/clear difficulty across the selection (mixed-state aware).
- The core card action relabels to "Details" and opens the drawer via a
  feature-detected global, falling back to the legacy modal when the
  drawer isn't mounted.

16 batch tests new; the P1 user-meta suite stays green.
tailwind.min.css rebuilt for the drawer's utility classes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nm7tHs1Yvjjtnnu4nzJgdN

* fix(v3): surface bulk-edit / save-details request failures instead of reporting success (PR #703 review)

Check the batch/write responses and show an fbNotify error (keeping selection and drawer) instead of unconditionally closing as success.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: byrongamatos <xasiklas@gmail.com>

static/v3/card-actions-core.js

@@ -23,11 +23,18 @@
     reg.register({
         id: 'core.edit-metadata',
         pluginId: 'core',
-        label: 'Edit metadata',
+        label: 'Details',
         placement: 'menu',
         order: 10,
         applies: (song) => !!(song && song.filename),
         run: (song) => {
+            // Prefer the v3 Details drawer (identity + personal difficulty / tags
+            // / notes); fall back to the legacy edit-metadata modal where the v3
+            // songs screen hasn't defined the opener (e.g. an older shell).
+            if (typeof window.__fbOpenSongDetails === 'function') {
+                window.__fbOpenSongDetails(song);
+                return;
+            }
             if (typeof window.openEditModal !== 'function') return;
             window.openEditModal({
                 f: song.filename, t: song.title || '', a: song.artist || '',