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>

PROJECT.md

@@ -2582,15 +2582,40 @@ inside a `<script type="module">` is a hard 404 the moment the same file is serv
   purpose — iOS already routes these through the system's own vibration setting.
   **Untested on hardware.** The simulator has no Taptic Engine, so every weight and gap below is a
   guess on paper and needs its own phone round before any of it is assumed good.
-- **SWIPE LEFT GOES BACK** in the menus. Every screen but the splash wears exactly one chevron, and
-  that button already knows where back is for its own screen — so the gesture finds the visible
-  `.chev` and clicks it rather than keeping a second map of the wizard that would drift the first
-  time a stage is added. Threshold 60 px, horizontal-dominant so the stats and board screens still
-  scroll. The `touchend` listener is deliberately **not passive**: a swipe that starts and ends
-  inside one of the big poster cards also produces that card's click, and `preventDefault` is what
-  stops the screen answering forward in the same frame the chevron walked it back.
-  **iOS convention is the opposite** (the system pop gesture drags rightward from the left edge).
-  Built to the brief as asked; flipping it is the sign on one comparison in `main.js`.
+- **SWIPE RIGHT GOES BACK** in the menus — the direction iOS's own pop gesture goes. (Built leftward
+  first, to the letter of the brief; Oliver flipped it the same hour: *"that's the iOS way"*. The
+  lesson is cheap and worth keeping: on a platform gesture, the platform's convention beats the
+  literal wording of the request — say so up front rather than shipping it and flagging it after.)
+  Every screen but the splash wears exactly one chevron, and that button already knows where back is
+  for its own screen — so the gesture finds the visible `.chev` and clicks it rather than keeping a
+  second map of the wizard that would drift the first time a stage is added. Threshold 60 px,
+  horizontal-dominant so the stats and board screens still scroll. The `touchend` listener is
+  deliberately **not passive**: a swipe that starts and ends inside one of the big poster cards also
+  produces that card's click, and `preventDefault` is what stops the screen answering forward in the
+  same frame the chevron walked it back.
+- **SOUND, and it was broken twice over on the first shell build.** Oliver, minutes after it ran:
+  *"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, both now fixed, both worth knowing before the
+  next plugin:
+  1. **`fetch` responses from the app bundle are OPAQUE.** Capacitor serves `capacitor://localhost`
+     through a custom `WKURLSchemeHandler`, and `fetch` reports those as `status: 0, ok: false` —
+     with the full body present and decoding perfectly. `audio.js` guarded all three of its loads
+     with a plain `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 ever started, no sample ever 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, not a failure** — trust the status only when there is one,
+     so a real 404 still falls back. **Any future `!r.ok` guard on a bundle-relative fetch is this
+     same bug.** (`stats.js` is fine: its board calls go to the live host over real HTTPS.)
+  2. **The ring switch muted everything on device.** WKWebView's WebAudio runs in the SoloAmbient
+     session, which the hardware silent switch kills outright — a completely silent game on a phone
+     that lives on silent, with nothing on screen to explain it. `AppDelegate` now sets
+     `AVAudioSession .playback`, the games-and-media category. That is a shell-only fix; the web
+     build has no say in it, and it is a good part of why the shell is worth having for sound.
+
+  Confirmed in the shell after both fixes: the bed reaches `PLAYING`, the context is `running`
+  **with no gesture at all** (autoplay really is allowed in WKWebView, as LATER predicted), and the
+  `say()` fallback never fires. On the web, a genuinely missing file still falls back — checked.
 - **The app has no server behind it.** Inside the shell the page is served from the bundle
   (`capacitor://localhost`), so `fetch('api/scores')` and the netplay socket would have resolved
   against the app's own files. `config.NATIVE`/`config.API` and one branch in `net.js` point the