- music_source / spotify_connected / spotify_rate_limited were reading
a non-existent 'spotify' key on _status_cache and silently falling
through to the missing-value default (always 'unknown' / False).
Routed through the canonical accessors get_primary_source +
get_spotify_status now.
- added hydrabase_connected, youtube_available, hifi_instance_count,
and always_available_metadata_sources so the debug dump reflects
the full service surface
- removed a local re-import of get_spotify_status that was making
python 3.12 treat the name as function-scoped, breaking the new
lambda above it (NameError on free variable) — module-level import
already exists
11 endpoint-level tests pin music_source / spotify_* / hydrabase_* /
youtube_available / always_available_metadata_sources / hifi_instance_count
and the defensive fall-through paths when each lookup raises.
