Overview

This pull request fixes the Android USB permission-denial path so a denied permission request surfaces as a clear terminal disconnect instead of silently entering the reconnect path.

Before this change, SerialRadioTransport.onMissingPermission(...) logged the missing permission callback but did not notify the service layer. That left the selected USB device in a retry-oriented state even though Android had denied access for the current connection attempt.

This change reports USB permission denial as a structured transport disconnect reason, keeps user-facing copy out of the serial transport layer, and maps the reason through the existing connectionError flow at the service boundary.

Key Changes

• Added TransportDisconnectReason.UsbPermissionDenied as a machine-readable transport disconnect cause.
• Extended RadioTransportCallback.onDisconnect(...) to carry an optional structured disconnect reason.
• Updated the serial transport path so USB permission denial:
  • stops the current connection attempt,
  • reports a permanent disconnect,
  • passes TransportDisconnectReason.UsbPermissionDenied,
  • leaves user-facing copy selection to the service/UI layer.
• Mapped UsbPermissionDenied in SharedRadioInterfaceService to the existing connectionError flow.
• Preserved the early explicit-close guard before serial warning logs so expected close callbacks stay quiet.
• Added service coverage proving USB permission denial emits the expected error and moves the service to ConnectionState.Disconnected.

Testing

• Added SharedRadioInterfaceServiceLivenessTest coverage for USB permission denial.
• Verified the permission-denial path reports the expected connection error and ends in ConnectionState.Disconnected.

Migration Notes

• No user data migration is required.
• No USB address format changes are introduced.
• Existing transient USB unplug / cable-loss behavior remains unchanged.
• Existing explicit close behavior remains quiet.