pax 57a19f87ba gelbooru: re-add background prefetch for batch API fast path only
When _batch_api_works is True (Gelbooru proper with auth, persisted
from a prior session's probe), search() fires prefetch_batch in the
background. The batch tag API covers the entire page's tags in 1-2
requests during the time between grid render and user click — the
cache is warm before the info panel opens, so categories appear
instantly with no flash of flat tags.

Gated on _batch_api_works is True (not None, not False):
  - Gelbooru proper: prefetches (batch API known good)
  - Rule34: skips (batch_api_works = False, persisted)
  - Safebooru.org: skips (no auth → fetcher skips batch capability)

Rule34 / Safebooru.org / Moebooru stay on-demand: the ~200ms
per-click HTML scrape is unavoidable for those sites because their
only path is per-post page fetching, which can't be batched.
2026-04-09 20:01:34 -05:00
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