`gateway/mirror.py` captured `sessions.json` under the home that was live at
import. Under the multiplexed gateway one process serves every profile, so the
pre-migration fallback in `_find_session_id()` resolved every profile's lookup
against the launch profile's index — a `platform`+`chat_id` pair present in both
indexes returns the launch profile's session id, mirroring a delivery into a
session that belongs to another profile.
Only the fallback is affected: the primary `state.db` query goes through a bare
`acquire()`, which follows `get_hermes_home()` at call time and is already
profile-correct. The access is read-only, so nothing was written to the wrong
profile.
Applies the resolve pattern the rest of the repo already uses (gateway/hooks.py,
gateway/sticker_cache.py, tools/process_registry.py, tools/checkpoint_manager.py):
keep the module constant as the monkeypatch surface, snapshot it at import, and
re-resolve only when unchanged.
The added test reloads the module under a launch home and then serves a lookup
for a second profile; without the fix it returns `sess_launch` instead of
`sess_active`.
Fixes#112844
f27c719a93