iPhone: step probes + full hls.js error stream to server

The play-probe now lands (iPhone: iOS 18.7 Safari, hls.js path, MSE ok),
but the /stream XHR never reaches the server on the failing attempts —
impossible under the known code path. Instrument each step
(new-hls-ok / loadsource-called / attach-ok) and log EVERY hls.js error
(fatal+non-fatal, with retry counter) so the client timeline is visible
server-side. Also fixed JSV constant drift (was stuck at 10).
events endpoint: accept hls-err, forward step/fatal/details/buffer/retry/http.

static/app.js

@@ -1,5 +1,5 @@
 // app.js — ani-web frontend: search -> detail -> play, vanilla JS + hls.js
-const JSV = 10;  // bump with every app.js change; play-probe reports it so a
+const JSV = 12;  // bump with every app.js change; play-probe reports it so a
                  // stale-cache phone is detectable server-side
 // BASE = this page's directory, so the app works at / or behind a
 // prefixing reverse proxy (e.g. https://host/ani/)
@@ -915,14 +915,22 @@ async function play(ep_id, ep_no) {
       timeoutRetry: { maxNumRetry: 6, retryDelayMs: 1000, maxRetryDelayMs: 20000, backoff: "linear" },
       errorRetry:   { maxNumRetry: 8, retryDelayMs: 1000, maxRetryDelayMs: 20000, backoff: "linear" },
     } } });
+    // iPhone debugging: log EVERY hls.js error (fatal and not) so the
+    // client-side timeline is visible server-side
     hls.on(Hls.Events.ERROR, (_, data) => {
+      try { postEvent({type: "hls-err", jsv: JSV, fatal: data.fatal, details: data.details,
+        buffer: data.buffer || null, retry: data.retry ?? null,
+        http: data.response ? data.response.code : null}); } catch {}
       if (data.fatal) {
         stopHls();
         playerFail(data.details + (data.response ? ` (HTTP ${data.response.code})` : ""));
       }
     });
+    try { postEvent({type: "play-probe", jsv: JSV, step: "new-hls-ok"}); } catch {}
     hls.loadSource("/stream/" + s.token);
+    try { postEvent({type: "play-probe", jsv: JSV, step: "loadsource-called"}); } catch {}
     hls.attachMedia(v);
+    try { postEvent({type: "play-probe", jsv: JSV, step: "attach-ok"}); } catch {}
     }
     currentEp = {ep_id, ep_no, v};
     lastSavedPos = 0;