Review fix round 1 for lane F:
- The ScanState probe watcher is seeded at InitializeAsync from a platform-only
DiscoverHierarchy query (IGalaxyPlatformSource / GatewayGalaxyPlatformSource over the owned
repository client) and re-seeded on every deploy-watcher rediscovery. The runtime never
calls DiscoverAsync on a live driver, so per-platform host status was unreachable in
production. A failed fetch logs a Warning and never fails init; re-seeds coalesce so a
deploy during an in-flight pass still gets a pass that starts after it.
- EnsureEventPumpStarted refuses while the runtime is stopping, BEFORE reusing the live pump
(that pump belongs to the dying subscriber), and the production rebuild disposes any stale
pump before wiring the new subscriber.
- TeardownRuntimeAsync closes the MX session under the caller's token linked with a 5 s
SessionCloseDeadline, so a blackholed gateway cannot hold DriverInstanceActor.PostStop for 30 s.
- A runtime generation counter, bumped by every teardown, is re-checked before each Rebind
in ResubscribeAllAsync, so a replay-gap re-snapshot that straddles a teardown cannot
resurrect handles into the cleared registry.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty