Two follow-ups on top of the salvaged #46365 fix:
1. Tests: the salvaged tests injected the ephemeral MatrixAdapter via
sys.modules["gateway.platforms.matrix"], but Matrix migrated to a plugin
(#41112) and the fallback now imports from plugins.platforms.matrix.adapter.
Point the three sys.modules patches at the current module path so the
ephemeral-fallback tests actually exercise the injected fake adapter.
2. Harden the live-adapter lookup: split the gateway import guard from the
adapter lookup and log (instead of silently swallowing) when a runner
exists but adapters.get() raises. A silent fall-through there would
re-introduce the per-send reconnect/OTK-exhaustion storm this fix exists
to prevent (#46310). Documented that the live adapter is gateway-owned and
must not be disconnected, and why the ephemeral finally never touches it.
kshitijk4poor
fc7a01b6cb