docs: record 1.1 hard-won knowledge in CLAUDE.md; refresh README

CLAUDE.md:
- Download pipeline: leading aesthetic characters in artist names must be trimmed
  before the iTunes lookup (a missed match cascades into a wrong-duration YouTube
  grab), and an album tag is always written (defaulting to Singles) so Navidrome
  and the metadata editor agree.
- New Android section covering the traps this release cost the most time on: a
  BackHandler inside a NavHost destination loses back priority (overlay back must
  be registered at the app root), overlay state must live in the ViewModel rather
  than remember/rememberSaveable, bottomBar and ModalBottomSheet inset handling,
  reusing the Ktor client, global optimistic StarState, and iTunes artists having
  no artwork.

README: offline downloads also cover single songs and work without a server
connection; StarState added to the data/ listing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -14,7 +14,7 @@ Built with Vite + vanilla ES modules (web) and Jetpack Compose + Media3/ExoPlaye
 - **Playlists** — Create, rename, delete, add/remove tracks, and upload a cover (Web + Android).
 - **Importer & downloads** — Paste a Spotify / YouTube / YouTube Music / SoundCloud link to download via yt-dlp, with iTunes metadata enrichment and duplicate detection.
 - **Metadata editor** (web) — Edit tags + cover art; files are renamed/moved and Navidrome is rescanned on save.
-- **Offline** (Android) — Download albums/playlists to private storage; an Offline tab to play and manage them; downloaded tracks play from disk on every screen.
+- **Offline** (Android) — Download albums, playlists, or single songs to private storage; an Offline tab to play and manage them (works without a server connection); downloaded tracks play from disk on every screen.
 - **Audiobookshelf** — Browse and stream audiobooks with chapter navigation, speed control, sleep timer, and progress sync.
 
 Web is an installable PWA (themes, German UI); Android is native Jetpack Compose + Media3/ExoPlayer with a mini player, media/ABS notifications, and Android Auto. See [CHANGELOG.md](CHANGELOG.md) for the full web/Android parity matrix.
@@ -65,7 +65,7 @@ NovaSonic/
 ├── android/                   # Native Android app (Jetpack Compose + Media3)
 │   └── app/src/main/kotlin/com/novasonic/app/
 │       ├── api/               # SubsonicClient, AbsClient, LrcLibClient, ItunesClient
-│       ├── data/              # PrefsStore (DataStore), MusicRepository
+│       ├── data/              # PrefsStore (DataStore), MusicRepository, StarState
 │       ├── offline/           # Room DB, DAO, OfflineRepository, DownloadWorker (offline downloads)
 │       ├── player/            # PlayerController, MusicService (Media3)
 │       ├── ui/