Nothing was landing in the metadata cache browser because the
metadata_cache_entities / metadata_cache_searches tables did not exist, so every
cache write no-op-ed. Root cause: _add_metadata_cache_tables short-circuited on a
marker-only guard (if the metadata_cache_v1 marker row exists, return). After a
DB corruption-recovery the small metadata table (with the marker) survived but
the large cache tables did not, so the stale marker permanently blocked the
idempotent CREATE TABLE IF NOT EXISTS and the cache was dead forever.
Guard now skips only when the marker is set AND the tables actually exist, so a
stale marker self-heals: the tables are re-created on the next init.
Tests: marker present but tables dropped -> re-created; marker + tables present
-> no-op (idempotent).
BoulderBadgeDad