austinried 2b104f1387 download a song to the device and play it from there ...

First block of #65: the state machine, the platform download engine, a
single-song download from the song context menu, the downloaded indicator in
song lists, and local-first playback.

- `song_downloads`, keyed `(sourceId, songId)` with CASCADE on the source, and
  the 16 -> 17 migration.
- `DownloadEngine` over `android.app.DownloadManager`, with a fake for tests.
  Files land in app-specific external storage at
  `.../Music/downloads/<sourceId>/<songId>`, plus a `.nomedia` so media scanners
  on pre-Android-10 devices leave them alone.
- `DownloadRepository` enqueues, mirrors progress by polling, cancels, deletes
  and reconciles on start and on source change: a queued row whose engine entry
  is gone is started again, a completed row whose file is gone becomes failed
  rather than being resurrected, and files with no row are swept.
- Playback prefers the downloaded file: the media item build takes the local URI
  when the download is complete and leaves it unclipped.
- Deleting a download reloads the player window at its position, so the item
  falls back to streaming instead of failing mid-read.
- Deleting a source cancels its downloads and removes their files.

Downloads are the system's own notifications and stay off metered networks for
now. Artwork, bulk downloads and the management screen are later blocks.

2026-10-04 00:30:01 +00:00

..

com.subtracks.data.db.SubtracksDatabase

download a song to the device and play it from there

2026-10-04 00:30:01 +00:00