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/i18n/locales/ru.json

@@ -735,7 +735,7 @@
   "STATION TAG": "ТЕГ СТАНЦИИ",
   "DRAG TO TUNE": "ТЯНИТЕ ДЛЯ НАСТРОЙКИ",
   "TAB PREVIEWS · ENTER / SPACE SELECTS": "TAB — ПРОСМОТР · ENTER / SPACE — ВЫБОР",
-  "Audio connects directly to the broadcaster after you press play. Your IP is visible to that broadcaster.": "После нажатия «Пуск» звук идёт напрямую от вещателя, и ему виден ваш IP-адрес.",
+  "Audio connects directly to the broadcaster when you press play, finish tuning or choose a station on the globe. Your IP is visible to that broadcaster.": "Звук идёт напрямую от вещателя после нажатия «Пуск», завершения настройки или выбора станции на глобусе. Вещателю виден ваш IP-адрес.",
   "Internet radio and local SDR": "Интернет-радио и локальный SDR",
   "Filter stations by station tag": "Фильтровать станции по тегу",
   "CONTEXT": "КОНТЕКСТ",