[Rafa7046]

Problem

GET /context/tracks?uri=spotify:station:track:<id> never becomes ready. It keeps answering ready: false, length: 0, cached: 0, while albums and single tracks list fine (metadata enabled).

Reproduction

1. Call GET /context/tracks?uri=spotify:station:track:4cOdK2wGLETKBW3PvgPWqT and keep polling it.
2. The response stays ready: false, length: 0 for good, and about every 2 s the daemon logs:

level=warning msg="failed enumerating context: spotify:station:track:4cOdK2wGLETKBW3PvgPWqT" error="failed fetching page 2: failed fetching next page: invalid status code from page at hm://radio-router/v3/tracks/spotify:station:track:4cOdK2wGLETKBW3PvgPWqT?...&count=50&prev_tracks=...: 404"

The page indices in that log start at 0. Pages 0 and 1 load; the failing request lists their 50 tracks as prev_tracks. Then the radio-router answers 404 for page 2. enumerateContextTracks treats any page error as fatal, so it throws away the tracks it already has. Nothing is cached, and the next poll starts the same enumeration again.

Fix

Stations get a narrow exception in enumerateContextTracks. A station is an endless radio context, so there is never a complete listing to wait for. The radio-router may also answer 404 for a later page, and when it does, the pages it already served are all there is. So for a spotify:station: context that has already yielded tracks, a page failure now ends the listing with the tracks fetched so far, the same way the end of the context or the page cap does.

Everything else keeps the current behaviour:

• A station failure before any track was fetched is still an error, so an empty listing is never cached as ready.
• A cancelled or timed-out enumeration (ctx.Err() != nil) is still an error, so a cut-off listing is never cached as the whole one.
• Every other context type still fails the whole enumeration on any page error. A transient failure on a long playlist is retried, not cached as a short listing.

Only the context listing and its metadata sweep use this function. Autoplay and playback are unchanged.

Tests

• TestEnumerateContextTracksKeepsStationPagesBeforeAFailure: a station's page 0 yields tracks and page 1 fails. Result: page 0's tracks, no error.
• TestEnumerateContextTracksReportsStationErrorsBeforeAnyTrack: a station's page 0 is empty and page 1 fails. Still an error.
• TestEnumerateContextTracksReportsStationCancellation: a station cancelled after a good page. Still an error.
• TestEnumerateContextTracksReportsLaterPageErrors: a playlist whose page 1 fails still errors, as before.
• TestEnumerateContextTracksReportsPageErrors (existing): a failing page 0 still errors.
• TestContextTracksHandlerListsStationFirstPage: through the API handler, a station whose page 1 fails answers ready: true with length == cached == the count from page 0. Without the fix it stays not-ready.

go test -tags "test_unit test_integration" ./..., go vet and gofmt -l . are clean.