Three call sites built near-identical httpx.AsyncClient instances:
the cache download pool, BooruClient's shared API pool, and
detect_site_type's reach into that same pool. They differed only
in timeout (60s vs 20s), Accept header (cache pool only), and
which extra request hooks to attach.
core/http.py:make_client is the single constructor now. Each call
site still keeps its own singleton + lock (separate connection
pools for large transfers vs short JSON), so this is a constructor
consolidation, not a pool consolidation.
No behavior change. Drops now-unused USER_AGENT imports from
cache.py and base.py; make_client pulls it from core.config.
