feat(library): effective genre falls back to MusicBrainz enrichment (#949)

* feat(library): effective genre falls back to MusicBrainz enrichment

Converted packs rarely carry a genres manifest key — on Byron's real
library 1188/1190 songs had no genre, starving the genre facet and the
career passport rack (2 usable genres) while song_enrichment already
held MB genres for 636 matched songs.

The effective-genre expression now resolves: per-song override → pack
genre → json_extract(enrichment.genres, '$[0]') for MATCHED rows only
(review/failed candidates could carry the wrong recording's genres).
Same fast-path gating as before: the plain indexed column is used
unless overrides or enrichment genres actually exist; stand-in DBs
without the table degrade via the OperationalError guard. Career
passports pick this up automatically through _effective_genre_expr().

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs: changelog names manual rows in the enrichment fallback

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

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

CHANGELOG.md

@@ -8,6 +8,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- **Genres fall back to MusicBrainz enrichment** — the effective genre now
+  resolves override → pack genre → the enrichment match's primary genre
+  (matched or user-pinned manual rows only). Converted packs rarely carry a `genres` manifest key,
+  which starved the library genre facet and career passports on real
+  libraries; with the fallback, every enriched song's genre is browsable and
+  passport-able immediately, and coverage grows as enrichment runs.
 - **Badge ceremony in the venue** — earning a genre badge now stages a moment:
   the crowd layer erupts (new public `v3VenueCrowd.celebrate()` — instant
   ecstatic loop bypassing the stability/dwell hysteresis, plus a cheer stinger;