The PR's race test slowed save_config and hoped for an interleave, and
called the six handlers as web_server attributes that no longer exist
(web_server.py is a facade over web_routers/). Its second test read
inspect.getsource() for the lock name — a change-detector on source text.
Replace both with two invariant tests that drive the real endpoints via
TestClient and FORCE the interleaving: writer 1 is held inside save_config
until writer 2 has run load_config (or the lock kept it out). Unlocked the
second save erases the first mutation; locked the writes serialize.
Verified: reverting hermes_cli/web_routers/ to main fails both tests
(KeyError 'providers' / 'aggregator' = the lost write), the fix passes.
131ea24026