Bring back the tuner-release and connecting-label Radio fixes

Restore the two fixes the previous commit moved out:

- A tuner release onto a station the directory dropped mid-drag stops the
  stream the drag paused, publishing one state with the gesture's origin,
  so the button reads PLAY and a voice handoff is cancelled.
- The transport buttons offer Pause while a stream connects, matching
  what a click does.

Their tests now use the shared Radio layer harness.

docs/CURRENT-STATE.md

@@ -4774,7 +4774,8 @@ result reads enabled state from the manager and audio state from the Radio
 module. Voice Pause is a playback-only no-op while the layer is disabled; it
 never enables Radio and reports a fulfilled-false pause as failure. A
 newer-response or user-origin Stop still cancels stale handoff work, as do a
-user Pause and a user Previous/Next that only selects another station.
+user Pause, a user Previous/Next that only selects another station, and a tuner
+release onto a station the directory no longer has.
 Only a newer user turn or session teardown aborts the complete active-tool set.
 A cancelled turn cannot publish a late Radio playback request. Dedicated Radio
 controls and generic layer-visibility commands both forward cancellation.