feat(v3 library): genre field in the Fix-metadata popup

[ChrisBeWithYou]

Adds Genre as a fifth field in the popup's Details tab (stacked on #779 → #778 → #777).

What

• Genre gets the same treatment as the other fields — edit, lock (pin against auto-match), revert, and Yours/Pack provenance — backed by the existing override store (which already allowed genre).
• Made it actually useful: the genre filter and facet (/api/library/genres + the genre= filter) now resolve the per-song override — effective genre = your override else the scanned pack genre — so a corrected or added genre is immediately browsable. Guarded on _has_genre_overrides() so the common no-override case stays on the plain indexed column (zero cost).
• Genre stays a library-only overlay — it is deliberately not a write-to-file field. WRITE_FIELDS (the four file-safe fields) is split from the five DETAIL_FIELDS, so Write to file writes title/artist/album/year and leaves the genre override in place; the copy says "genre stays a library-only tag."
• The Match→Details bridge (feat(v3 library): Match→Details "use these values" bridge #779) also carries a candidate's first genre into the field.

Why genre isn't written to the pack

POST /api/song/{fn}/meta (the write path) handles the four catalog fields; the feedpak genres list is a separate shape and genre works best as a fast, reversible library-side facet (fix it, browse by it, never touch the file). Locking still protects it from auto-match.

Testing

• New tests: the effective-genre facet + filter surface/return an overridden song; a value-less genre lock doesn't invent an effective genre. Full test_field_overrides + test_library_filters green (57).
• Verified live on the testbed: overriding a city-pop pack's genre to "City Pop" makes it appear in the facet and filterable (1 song matched), cleared cleanly.

Stacks on #779 → #778 → #777. Merge bottom-up.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Genre overrides now count in library browsing and filtering, so the app shows the effective genre instead of only the stored file value.
  • The metadata review screen now displays Genre in the pending details view.
• Bug Fixes
  • Writing metadata now preserves genre overrides instead of clearing them.
  • Genre lookups and filters now stay consistent when a song has an overridden genre value.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f6e354b6-e9e0-4c02-b7a7-6a6cd84ceb32

📥 Commits

Reviewing files that changed from the base of the PR and between 6397a95 and 007c435.

📒 Files selected for processing (3)

• server.py
• static/v3/match-review.js
• tests/test_field_overrides.py

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📝 Walkthrough

Walkthrough

This PR makes genre queries use override-aware effective values on the server, shows candidate genre in the match-review Details view, keeps genre out of file writes, and adds API tests for facet/filter behavior.

Changes

Genre override support

Layer / File(s)	Summary
Effective genre SQL expression and query wiring server.py	Adds an override-aware SQL expression preferring per-song genre overrides when present, and uses it for genre filtering and the /api/library/genres facet query.
Match-review Details genre display and write-to-file exclusion static/v3/match-review.js	Adds genre to the Details field list, pre-fills it from candidate genres, updates helper text, and limits write-to-file plus post-write cleanup to non-genre fields.
API tests for genre override facet and filter behavior tests/test_field_overrides.py	Adds tests verifying override-driven genre facets and filtering, and that lock-only genre overrides do not change the effective genre expression.

Estimated code review effort: 2 (Simple) | ~15 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant API as /api/library/genres
  participant MetadataDB
  participant DB as SQLite

  Client->>API: GET /api/library/genres
  API->>MetadataDB: resolve effective genre expression
  MetadataDB->>DB: query distinct effective genres
  DB-->>MetadataDB: genre values
  MetadataDB-->>API: facet list
  API-->>Client: genres list

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Related issues: None found.

Related PRs: None found.

Suggested labels: backend, frontend, tests

Suggested reviewers: None specified.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/v3-genre-in-details

⚔️ Resolve merge conflicts

• Resolve merge conflict in branch feat/v3-genre-in-details

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[ChrisBeWithYou]

📋 Merge order — metadata-curation epic (7 PRs)

1. feat(v3 library): "Fix metadata" popup — per-song override + lock, cover picker, MusicBrainz + AcoustID #777 — Fix-metadata popup
2. feat(v3 library): "Write to file" in the Fix-metadata popup #778 — Write to file
3. feat(v3 library): Match→Details "use these values" bridge #779 — Match→Details bridge
4. feat(v3 library): genre field in the Fix-metadata popup #780 — Genre in Details
5. feat(v3 library): persistent "no match" badge + Unmatched quick filter #781 — No-match badge + Unmatched filter (independent of 1–4 — fine to merge any time)
6. feat(v3 library): batch→popup handoff + English-base romaji (metadata-curation capstone) #782 — Batch→popup handoff + romaji (capstone)
7. feat(v3 library): searchable Cover Art Archive picker in Change-cover #783 — Searchable cover picker

#778–#780 are stacked (each based on the branch above), so GitHub re-points each to main automatically as the previous one merges — just merge #777 → #778 → #779 → #780 top-down. #781 is independent (base: main).

⚠️ Hold #782 and #783 until #777–#781 are all in main. #782's branch is a combined branch that already contains #777–#781, so merging it early would double-merge the stack. Once #777–#781 land, the author will rebase #782 (then #783) onto main — they shrink to just their own commits — and they're then ready to merge.