Sound was dead in the app because status 0 is not a failure; and back is a swipe to the RIGHT

Oliver on the first shell build: *"I don't hear any of the games sounds.. daniel the umpire is
synthesized which is horrible and no music is playing on start"* — two independent causes.

- **Opaque fetch.** Capacitor serves the bundle through a custom WKURLSchemeHandler, and `fetch`
  reports those responses as `status: 0, ok: false` with the whole body present and decoding
  perfectly. All three loads in `audio.js` guarded with `if (!r.ok) throw`, so inside the app every
  recorded sound failed at the door: the umpire fell through to the synthesized `say()`, no bed
  started, no sample played. The synthesized sfx kept working, which made it read as a mixing bug
  rather than a loader one. Fixed once, in the shared `bytes()` helper every audio fetch now routes
  through — a status of 0 is the ABSENCE of an HTTP status, so trust it only when there is one and
  a real 404 still falls back. Any future `!r.ok` on a bundle-relative fetch is this same bug.
- **The ring switch.** WKWebView's WebAudio runs in the SoloAmbient session, which the hardware
  silent switch mutes outright — a silent game on a phone that lives on silent, with nothing on
  screen to explain it. AppDelegate now sets AVAudioSession `.playback`, the games category.

Confirmed in the shell: the bed reaches PLAYING, the context is `running` with no gesture at all
(autoplay really is allowed in WKWebView, as LATER predicted), and `say()` never fires. On the web,
a genuinely missing file still falls back — checked both.

And the swipe flips: **right goes back**, the way iOS's own pop gesture goes (*"that's the iOS
way"*). Left now does nothing. Noted in PROJECT.md that on a platform gesture the platform's
convention beats the literal wording of the brief, and that is worth saying up front.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

index.html

@@ -661,6 +661,6 @@ if (location.hostname !== 'splatter-tennis.wuwi.one' && !window.Capacitor?.isNat
     </div>
   </div>
 </div>
-<script type="module" src="src/main.js?v=296"></script>
+<script type="module" src="src/main.js?v=297"></script>
 </body>
 </html>