feat(spotify): consolidate tools (9→7), add spotify skill, surface in hermes setup (#15154)

Three quality improvements on top of #15121 / #15130 / #15135:

1. Tool consolidation (9 → 7)
   - spotify_saved_tracks + spotify_saved_albums → spotify_library with
     kind='tracks'|'albums'. Handler code was ~90 percent identical
     across the two old tools; the merge is a behavioral no-op.
   - spotify_activity dropped. Its 'now_playing' action was a duplicate
     of spotify_playback.get_currently_playing (both return identical
     204/empty payloads). Its 'recently_played' action moves onto
     spotify_playback as a new action — history belongs adjacent to
     live state.
   - Net: each API call ships 2 fewer tool schemas when the Spotify
     toolset is enabled, and the action surface is more discoverable
     (everything playback-related is on one tool).

2. Spotify skill (skills/media/spotify/SKILL.md)
   Teaches the agent canonical usage patterns so common requests don't
   balloon into 4+ tool calls:
   - 'play X' = one search, then play by URI (not search + scan +
     describe + play)
   - 'what's playing' = single get_currently_playing (no preflight
     get_state chain)
   - Don't retry on '403 Premium required' or '403 No active device' —
     both require user action
   - URI/URL/bare-ID format normalization
   - Full failure-mode reference for 204/401/403/429

3. Surfaced in 'hermes setup' tool status
   Adds 'Spotify (PKCE OAuth)' to the tool status list when
   auth.json has a Spotify access/refresh token. Matches the
   homeassistant pattern but reads from auth.json (OAuth-based) rather
   than env vars.

Docs updated to reflect the new 7-tool surface, and mention the
companion skill in the 'Using it' section.

Tests: 54 passing (client 22, auth 15, tools_config 35 — 18 = 54 after
renaming/replacing the spotify_activity tests with library +
recently_played coverage). Docusaurus build clean.

toolsets.py

@@ -218,11 +218,10 @@ TOOLSETS = {
     },
 
     "spotify": {
-        "description": "Native Spotify playback, search, playlist, album, library, and activity tools",
+        "description": "Native Spotify playback, search, playlist, album, and library tools",
         "tools": [
             "spotify_playback", "spotify_devices", "spotify_queue", "spotify_search",
-            "spotify_playlists", "spotify_albums", "spotify_saved_tracks",
-            "spotify_saved_albums", "spotify_activity",
+            "spotify_playlists", "spotify_albums", "spotify_library",
         ],
         "includes": []
     },