[Mobile] Fix offline album track downloads after v1 SDK migration

[dylanjeffers]

Summary

Track downloads were failing in offline mode — the user-visible symptom is "clicks download, sees a track attempt, then a failure icon." This affects both individual track downloads (favoriting a track with auto-download on, or any other path that queues a single track) and tracks inside an album/collection download, because every track-job entry point lands in the same queue and is processed by the same worker.

Two compounding issues in downloadTrackWorker.ts, both effectively introduced by the v1 SDK migration (#13728):

1. downloadTrackAudio skipped the v1 pre-signed stream URL. It built the URL via sdk.tracks.getTrackStreamUrl(), ignoring track.stream.url. The v1 API returns a pre-signed stream URL (with mirrors) on the track itself; AudioPlayer prefers it for online streaming and only falls back to manual URL construction when stream.url is missing. The offline worker skipped that working path entirely, so it relied on the fallback for every track.

2. downloadTrackCoverArt was fatal. It threw when no artwork URI returned 200, and because cover art runs in all([cover, audio, json]), a single flaky artwork host failed the entire track download — even though audio is the only essential payload. The collection cover art download follows the opposite (best-effort) pattern; this PR brings the track version in line.

Plus downloadTrackAsync's catch block silently swallowed the error — no logs, no Sentry breadcrumb. That's why this had been hard to diagnose.

Why this fixes both individual tracks and collections

Every track-job source — requestDownloadCollectionSaga, requestDownloadFavoritedCollectionSaga, requestDownloadAllFavoritesSaga, watchSaveTrackSaga (standalone track favorite), watchAddTrackToPlaylistSaga, syncCollectionWorker — dispatches addOfflineEntries({ items: [..., { type: 'track' }, ...] }). The queue processor routes every type === 'track' job to a single downloadTrackWorker, which calls the two functions patched here. So both flows share the same broken code path.

Changes

• downloadTrackAudio: prefer track.stream.url (with mirror substitution), keep getTrackStreamUrl() + manual signing as a last-resort fallback. Mirrors AudioPlayer.tsx logic.
• downloadTrackCoverArt: best-effort — return silently if all URIs fail rather than throwing.
• Extract shared buildMirrorUris(primary, mirrors) helper used by both audio and cover art.
• Add a console.warn in the catch block of downloadTrackAsync so future failures are diagnosable instead of silent.

Test plan

• Offline mode → favorite a single track with "download all favorites" enabled. Track reaches SUCCESS, plays from local file.
• Offline mode → download an album you don't own (where you've favorited it). All tracks reach SUCCESS, audio plays from local file.
• Offline mode → download an album where the artwork host is degraded. Audio still downloads successfully; cover art is best-effort.
• Offline mode → download a single track via the track menu. Still works (no regression).
• Offline mode → toggle "Download all favorites." Track downloads succeed.
• Offline mode → play a downloaded track while offline. File-system playback still works.
• Gated content (USDC / NFT) → confirm the manual-URL fallback path still signs correctly when stream.url is unset.

🤖 Generated with Claude Code

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