Sibling site of the same class fixed in the previous commit: a failed
profile-store open during _init_session fell back to _get_db(), hydrating
and persisting a named-profile session's cwd row against the launch
state.db. Fail closed instead — skip the hydration (log a warning) so
nothing ever reads or writes the wrong profile's store. The other
profile-store open sites (_db_for_profile, _ensure_session_db_row,
_session_db) already degrade to None/skip and were left as-is.
A deferred agent build for a named-profile session swallowed a failed
profile-store open (except Exception -> session_db = None), so _make_agent
silently bound the launch _get_db() handle and every turn bled into the
wrong profile's state.db exactly when the profile store was briefly
unopenable. Opening the named profile then looked blank.
Route the open through _open_profile_session_db, which raises a clear
'profile session store unavailable' error instead; the deferred build's
existing except path turns that into agent_error + an error event, so the
user gets a clear failure and no agent turn against the wrong store.
Salvaged from #90219 (hardening half), adapted to main's current
deferred-build/_transfer_db_to_agent structure.
Related to #87723 and #89789. #88532 covered SessionStore only.
Teknium