Centralize mirrored playlist source reference normalization so edited links and IDs are stored consistently. Preserve URL-backed refresh refs, surface missing-source refresh failures, count background sync failures in pipeline summaries, and retry guarded automation skips after a short delay instead of losing a scheduled run. Add focused coverage for source refs, mirrored playlist source updates, refresh failures, and guarded retry behavior.
The "Clean Search History" automation card kept showing a stale
'DownloadOrchestrator' object has no attribute 'base_url' error
even after the underlying handler bug was fixed in 77d20e9. Root
cause is in the engine, not that handler: AutomationEngine only
captured uncaught exceptions into last_error. Handlers that
report failure by RETURNING {'status': 'error', ...} were treated
as successful from the engine's perspective, so subsequent
gracefully-failing runs never updated the row to reflect the
current state.
Both the timer (run_automation) and event (_handle_event_trigger)
paths now extract the error string from a result whose status is
'error', falling through 'error' -> 'reason' -> 'message' -> a
placeholder so last_error is never None on actual failures
regardless of which key the handler chose. Existing behaviour for
raised exceptions and successful runs is preserved.
Also normalizes _auto_clean_search_history's return key from
'reason' to 'error' so older deployed engines that only check
the canonical key still see the failure.
Adds 7 regression tests covering every result shape the engine
might receive.
