BuildAddressSpaceAsync now checks _disposed (throws ObjectDisposedException)
and tears down the previous alarm forwarder + clears the sink registry
before re-walking, so a Galaxy-redeploy rebuild does not leak the old
forwarder and double-deliver alarm transitions. Three regression tests
added: double-build does not double-fire, sink count is correct after
rebuild, and post-dispose call throws.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
6cec98caef