Keep Radio playback state consistent after a silent Next

Review follow-ups for HAL-722. A Next or Previous that only selects a
station now leaves nothing of the previous stream behind:

- Selecting another station without playing stops a paused or failed
  stream, so the panel, Stop, voice summaries and the audio element agree
  on "stopped". A fallback the caller armed for the new selection is kept.
- A silent UI step arms no broadcaster fallback, and a user Play of the
  selected station drops one left by a cancelled voice step. Voice steps
  pass `fallback: true` because voice starts the prepared playback later.
- A user step to another station emits a `select` playback control, and
  the realtime voice handoff treats it like Pause and Stop.
- A tuner release onto a station the directory no longer has 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.
- The privacy note names every action that connects to a broadcaster
  (play, finishing tuning, choosing a station on the globe) in all
  locales.

The Next/Previous layer tests live in src/data/radioNextState.test.mjs.

src/voice/gevActions.js

@@ -2211,7 +2211,11 @@ export async function controlRadio(
     if (!radioActionIsCurrent(options)) return cancelled(summarize);
     const prepared = state.selected
       ? true
-      : radio.cycleStation?.(1, { focus: false, autoplay: false });
+      : radio.cycleStation?.(1, {
+          focus: false,
+          autoplay: false,
+          fallback: true,
+        });
     return {
       ok: Boolean(prepared),
       action: 'control_radio',
@@ -2235,6 +2239,7 @@ export async function controlRadio(
     const selected = radio.cycleStation?.(action === 'next' ? 1 : -1, {
       focus: false,
       autoplay: false,
+      fallback: true,
     });
     return {
       ok: Boolean(selected),