Pause Bluetooth discovery during pairing

[itsMattGuenther]

The Bluetooth panel keeps discovery active while it starts an outgoing pair or connection. On adapters where inquiry competes with connection paging, that can make the attempt time out; because omarchy-bluetooth-device discarded every failure status, the panel then returned to idle without explaining what happened.

This pauses panel-owned discovery before pair/connect actions, keeps the cached available-device row visible during the pause, and observes the helper process so failures produce an actionable retry message. The helper now returns failure immediately instead of continuing to trust and connect a device that did not pair.

Fixes #8614

Validation:

• bash test/shell.d/bluetooth-test.sh
• Loaded the checkout in the running Omarchy shell and verified the connection-failure state renders without clipping or stale busy state
• Exercised the revised helper against a real Xbox controller and an unavailable address