try_compose_from_cache was returning True on ANY partial cache hit
(even 1/38 tags). ensure_categories then saw non-empty
tag_categories and returned immediately, leaving the post stuck at
1/38 coverage. The bug showed on Rule34: post 1 got fully scraped
(40/40), its tags got cached, then post 2's compose found one
matching tag and declared victory.
Fix: try_compose_from_cache now returns True ONLY when 100% of
unique tags have cached labels (no fetch needed). It STILL
populates post.tag_categories with whatever IS cached (for
immediate partial display), but returning False signals
ensure_categories to continue to the fetch path.
This is the correct semantic split:
- populate → always (for display)
- return True → only when complete (for dispatch)
Verified:
Rule34: 40/40 + 38/38 (was 40/40 + 1/38)
Gelbooru: 55/56 + 49/50 (batch API, one rare tag)
Safebooru.org: 47/47 + 47/47 (HTML scrape, full)