[AndrewDi]

Summary

Add a new Plugins/AppleMusicLyrics/ plugin that shows frosted-glass desktop lyrics in the top-right corner while Apple Music plays. The plugin reads lyric documents already cached by Music.app locally, so it needs no Apple account, network request, or extra permission.

The floating window is a borderless NSPanel with an NSVisualEffectView (.hudWindow material) that stays on top without activating. Track and playback position are polled every 0.5 s from Music.app, and lyrics are matched by title, artist, album, and duration against the cached catalog responses.

Features

• Configurable appearance: font size, background opacity, text opacity (independent), corner radius, text color, and next-line visibility.
• Karaoke rendering: per-word sung/upcoming highlighting with a fallback whole-line gradient when per-word timings are absent. A 逐字渲染 / Karaoke rendering toggle lets users opt out; the description notes Apple Music's timing is approximate.
• Draggable window: an opt-in drag toggle that persists the window position across launches.
• Localization: 12 languages (zh-Hans, zh-Hant, en, ar, de, es, fr, ja, ko, pt, ru, tr).
• Tests: 23 focused unit tests covering TTML parsing, cache lyric matching, karaoke rendering, text-color opacity scaling, and settings persistence/reset.

Documentation

• docs/plugins/apple-music-lyrics.md: plugin guide with settings and manual verification steps.
• README.md / README.zh-CN.md: feature paragraph in both languages.
• changes/unreleased/apple-music-lyrics-plugin.md: changelog fragment.
• docs/plugins/preferences-backup-inventory.md and site/src/generated/plugins.json: regenerated metadata.

Validation

• ✅ make validate-changelog and make validate-localization pass.
• ✅ 23 focused unit tests pass.
• ✅ Adhoc-signed build succeeds; plugin dynamically loads in the host app.
• ✅ Manual verification: window appears at top-right, karaoke sung/upcoming contrast is visible and can be toggled off, drag position persists across relaunch.

Notes

• docs/plugins/catalog.json is intentionally left untouched (it is a signed release catalog regenerated by the release flow).