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),

src/voice/gevActions.test.mjs

@@ -1850,7 +1850,7 @@ test('voice Radio resolves Austin and exposes semantic selection, volume, pause,
   assert.equal(result.radioAction, 'play');
   assert.equal(result.stationId, 'nearest');
   assert.equal('station' in result, false);
-  assert.deepEqual(calls.at(-1), ['cycle', 1, { focus: false, autoplay: false }]);
+  assert.deepEqual(calls.at(-1), ['cycle', 1, { focus: false, autoplay: false, fallback: true }]);
 
   for (const invalidCoordinates of [
     { latitude: null, longitude: null },

src/voice/gevRealtime.test.mjs

@@ -593,46 +593,55 @@ test('replacement input invalidates an in-flight Radio preflight immediately', (
   assert.equal(controller.radioHandoffEpoch, priorEpoch + 1);
 });
 
-test('direct Radio pause or stop cancels a pending voice handoff', async () => {
-  const order = [];
-  let playbackControl = null;
-  const ui = {
-    root: { dataset: {}, classList: { remove() {} }, querySelectorAll: () => [] },
-    status: { textContent: '' },
-    detail: { textContent: '', title: '' },
-    errorDetail: { textContent: '' },
-  };
-  const controller = new GevRealtimeController({
-    ui,
-    runner: async () => ({ ok: true }),
-    radioLayer: {
-      subscribePlaybackControls(listener) {
-        playbackControl = listener;
-        return () => { playbackControl = null; };
+for (const [name, control, message] of [
+  ['direct Radio pause or stop cancels a pending voice handoff', 'stop', 'the explicit stop remains authoritative'],
+  [
+    'a direct Radio Next that does not play cancels a pending voice handoff',
+    { action: 'select', origin: 'user', attemptId: null },
+    'the user selection is not overridden by voice playback',
+  ],
+]) {
+  test(name, async () => {
+    const order = [];
+    let playbackControl = null;
+    const ui = {
+      root: { dataset: {}, classList: { remove() {} }, querySelectorAll: () => [] },
+      status: { textContent: '' },
+      detail: { textContent: '', title: '' },
+      errorDetail: { textContent: '' },
+    };
+    const controller = new GevRealtimeController({
+      ui,
+      runner: async () => ({ ok: true }),
+      radioLayer: {
+        subscribePlaybackControls(listener) {
+          playbackControl = listener;
+          return () => { playbackControl = null; };
+        },
+        playForVoice: async () => {
+          order.push('radio-play');
+          return true;
+        },
+        stopPlayback: () => order.push('radio-stop'),
       },
-      playForVoice: async () => {
-        order.push('radio-play');
-        return true;
-      },
-      stopPlayback: () => order.push('radio-stop'),
-    },
-  });
-  controller.debugLog = () => {};
-  controller.dc = {
-    readyState: 'open',
-    send() {},
-    close() { order.push('voice-stop'); },
-  };
-  controller.pendingRadioPlaybackResult = { ok: true, radioPlaybackRequested: true };
+    });
+    controller.debugLog = () => {};
+    controller.dc = {
+      readyState: 'open',
+      send() {},
+      close() { order.push('voice-stop'); },
+    };
+    controller.pendingRadioPlaybackResult = { ok: true, radioPlaybackRequested: true };
 
-  playbackControl('stop');
-  await controller.handleRealtimeEvent({
-    data: JSON.stringify({ type: 'response.done', response: { status: 'completed' } }),
-  });
+    playbackControl(control);
+    await controller.handleRealtimeEvent({
+      data: JSON.stringify({ type: 'response.done', response: { status: 'completed' } }),
+    });
 
-  assert.equal(controller.pendingRadioPlaybackResult, null);
-  assert.deepEqual(order, [], 'the explicit stop remains authoritative');
-});
+    assert.equal(controller.pendingRadioPlaybackResult, null);
+    assert.deepEqual(order, [], message);
+  });
+}
 
 test('confirmed manual Radio playback closes active voice without stopping Radio', () => {
   const order = [];

src/voice/realtimeRadio.js

@@ -65,7 +65,7 @@ export class RealtimeRadio {
             : control || {};
         if (
           event.origin === 'user' &&
-          (event.action === 'pause' || event.action === 'stop')
+          ['pause', 'stop', 'select'].includes(event.action)
         ) {
           this.cancelRadioHandoff();
         } else if (