UnobservedConnectivity

The no-observer ConnectivityObserver: publishes null forever, so a seam built on it reports the roleless-availability FabricAvailability.Unknown floor and never a fabricated verdict.

This is the default on every loom, so wiring nothing changes nothing — it is the identity element of this feature, not a tuning knob that suppresses a working observer.

Exposed through asStateFlow for the same reason StaticUnknownCapability is in :kuilt-core: without it a consumer could downcast this one process-wide value to MutableStateFlow and move every unobserved seam's capability at once.