Addresses review feedback on the snapshot approach:
1. Class-instance mutable state
The snapshot only covers primitives + collections + None. Class
instances (DualCache, LLMClientCache) weren't reset between tests,
so in-place cache mutations could leak. Can't deepcopy these — they
hold thread locks — but they expose flush_cache(). Collect every
module attribute whose value implements flush_cache() at conftest
import, and invoke it per-test alongside the snapshot restore.
2. Silent skips are now warnings
_snapshot_mutable_state and _restore_mutable_state previously
swallowed exceptions, so if a future attr gained a property without
a setter (or other non-round-trippable state), an isolation gap
would have no signal. Emit warnings.warn on each failure path.
3. Docstring
Explicitly documents what IS and IS NOT reset, and tells authors to
use monkeypatch.setattr() for in-place mutations of instances
without flush_cache() (ProxyLogging, JWTHandler, etc.).
Yuneng Jiang
4b3f5d7f81