d2a0b7d780
First of three stages for system-playlist sample-history dedup (Fable #415, server-side rotation per the operator's choice). Schema (migration 0027): - play_events.source (nullable text): which surface a play came from. 'for_you' / 'discover' feed rotation; NULL for library / user-playlist / radio / Subsonic. - system_playlist_rotation_state(user_id, playlist_kind, played_track_ids uuid[], rotation_started_at, updated_at): the per-(user,kind) set of already-heard tracks this rotation. Ingest: - New RecordPlayStartedWithSource on the writer; RecordPlayStarted is now a thin source="" wrapper so the frozen Subsonic shim is untouched (no signature ripple). - When source is a known system kind, the same txn appends the track to rotation state (AppendRotationPlayed keeps the array a set via the conflict CASE). - /api/events play_started accepts an optional "source". No serve-behavior change yet — Stage 2 makes shuffle prefer the unplayed tail + resets on exhaustion; Stage 3 wires the clients to send source and consume the rotation-aware order. Tests: rotation appends + dedupes for a system source; source-less play writes no rotation row. (Existing RecordPlayStarted tests are unchanged — same wrapper signature, identical behavior at source="".) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>