Document the admin lyric editor, the lyrics skills and the LRCLIB matching guards

CLAUDE.md

@@ -403,6 +403,35 @@ Local DB file: `server/data/ytplayer.db` (gitignored). `BUILD_TAG` is computed f
 Skills live in `.agents/skills/` (symlinked into `.claude/skills/`):
 - **deploy-prod** — the Dokploy deploy + buildTag verification flow (manual-only; use for any "deploy"/"release" request).
 - **mobile-app-ui-design** — UI/UX design work on the PWA screens.
+- **lyrics-lookup** — fill in songs that have NO lyrics (LRCLIB → agy web search → local faster-whisper).
+- **lyrics-regenerate** — back up, then replace wrong/mistimed lyrics from LRCLIB (`scripts/lyrics/lrclib_regen.py`).
+
+### Matching a song on LRCLIB (learned the hard way)
+`/api/streams` gives the YouTube **channel**, not the artist, so a title+artist
+query finds nothing for a lyric-video channel ("Integrity Worship", "Christian
+Lyrics") — `lrclib_lookup` falls back to a title-only search and then ranks
+candidates whose artist *verifies* 50 points above those that don't. Two guards
+sit on the result, and both exist because they caught a real wrong song:
+- `artist_ok()` ignores `GENERIC` words. Channel "**Christian** Lyrics" once
+  vouched for a track featuring **Christian** Burns (Nicky Romero, "Still the
+  Same Man"). Never verify an artist on a word that says nothing about who
+  recorded the song.
+- `title_run()` compares **whole words, never substrings** — "Still" is a
+  substring of "(You Can Still) Rock in America", and a one-word title is
+  rejected outright. It gates the `LENGTH` rule (same title, within 3 s of the
+  same length ⇒ accept even when the artist can't be checked).
+An unverified match is printed as `UNSURE` and skipped; `--loose` overrides that
+and is almost always the wrong answer.
+
+### Admin lyric editor (`frontend/admin.html`)
+`/admin?v=<id>` (or the Edit/Lyrics buttons) opens a song with its audio from
+`/api/streams`, the waveform from `/api/media/:id/peaks`, and one row per line:
+**Set** stamps the playhead, ±0.2 s nudges, **Tap mode** stamps the highlighted
+line on Space and walks down, plus shift-all, line/section/cue kinds, a ✎ Text
+LRC view and a ⤓ LRCLIB pull. Saves are optimistic (`baseRev`, 409 → keep
+mine / load theirs). **Rows are built once per load and then only their classes
+and values change** — re-rendering on every tick would steal focus from the
+field being typed in and reset the scroll position.
 
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