Minor from the final fix wave: refresh_from used to FAMILIES.clear()
then .update(merged) — a concurrent detect_codes/family_of read
(the chat runs each turn in a threadpool worker) could observe an
empty registry in the window between those two calls. Now
FAMILIES.update(merged) first, then delete whatever key isn't in the
new merge — every in-between state is old UNION new, never empty.
Also fixes the FAMILIES module docstring, which still said "the chat
sees hand families only" — stale since Task 1 (P49) wired
llm.evidence.warm/_connect to call refresh_from on every replica
(re)open, at API startup and again before every detect_codes call.
New tests: a stale key not in the new merge is dropped by the end of
refresh_from; refresh_from never calls FAMILIES.clear() (verified by
swapping in a dict subclass whose clear() raises).
aa108797a2