fix: unblock speaker page audio when loadedmetadata never fires on opus blob

Stop gating the UI on the blob's loadedmetadata (Firefox never fires it for
large Ogg/Opus blobs). Release audioLoading right after load(), seed duration
from getSession().audio_duration / max turn end, and fall back to the direct
audio URL (HTTP Range streaming) via an 8s readyState check or blob onerror.
playAt waits for loadeddata/canplay instead of audioLoading.

frontend/src/pages/Speakers.tsx

@@ -18,6 +18,8 @@ export default function Speakers() {
   const audioRef = useRef<HTMLAudioElement>(null);
   const paletteRef = useRef(new Map<string, string>());
   const blobUrlRef = useRef<string | null>(null);
+  const directRef = useRef(false);
+  const fallbackTimerRef = useRef<number | null>(null);
 
   const [audioLoading, setAudioLoading] = useState(true);
   const [audioProgress, setAudioProgress] = useState(0);
@@ -31,16 +33,35 @@ export default function Speakers() {
       sp.forEach((s: any) => (n[s.raw_label] = s.display_name || ""));
       setNames(n);
     });
-    api.getTurns(id!).then(setTurns);
+    api.getTurns(id!).then((tr) => {
+      setTurns(tr);
+      setDuration((d) => d || tr.reduce((m, t: any) => Math.max(m, t.end || 0), 0));
+    });
+    api.getSession(id!).then((s) => {
+      if (s?.audio_duration) setDuration((d) => (d > 0 ? d : s.audio_duration));
+    });
   };
   useEffect(load, [id]);
 
+  const useDirectAudio = () => {
+    const audio = audioRef.current;
+    if (!audio) return;
+    directRef.current = true;
+    if (blobUrlRef.current) {
+      URL.revokeObjectURL(blobUrlRef.current);
+      blobUrlRef.current = null;
+    }
+    audio.src = api.audioUrl(id!);
+    audio.load();
+  };
+
   useEffect(() => {
     if (!id) return;
     setAudioLoading(true);
     setAudioProgress(0);
     setTotalKnown(false);
     setAudioError(null);
+    directRef.current = false;
     let cancelled = false;
     const url = api.audioUrl(id);
 
@@ -52,7 +73,7 @@ export default function Speakers() {
         const total = parseInt(res.headers.get("Content-Length") || "0", 10);
         setTotalKnown(total > 0);
         const reader = res.body!.getReader();
-        const chunks: Uint8Array[] = [];
+        const chunks: BlobPart[] = [];
         let received = 0;
 
         while (true) {
@@ -71,17 +92,29 @@ export default function Speakers() {
         const audio = audioRef.current;
         if (!audio || cancelled) {
           URL.revokeObjectURL(blobUrl);
+          blobUrlRef.current = null;
           return;
         }
 
-        await new Promise<void>((resolve, reject) => {
-          audio.onloadedmetadata = () => resolve();
-          audio.onerror = () => reject(new Error("Audio decode failed"));
+        audio.onerror = () => {
+          if (cancelled) return;
+          if (directRef.current) {
+            setAudioError("Audio decode failed");
+            setAudioLoading(false);
+          } else {
+            useDirectAudio();
+          }
+        };
+
         audio.src = blobUrl;
         audio.load();
-        });
-
         if (!cancelled) setAudioLoading(false);
+
+        fallbackTimerRef.current = window.setTimeout(() => {
+          if (cancelled || directRef.current) return;
+          if (audio.readyState >= 2) return;
+          useDirectAudio();
+        }, 8000);
       } catch (err: any) {
         if (!cancelled) {
           setAudioError(err.message || "Failed to load audio");
@@ -92,6 +125,10 @@ export default function Speakers() {
 
     return () => {
       cancelled = true;
+      if (fallbackTimerRef.current) {
+        clearTimeout(fallbackTimerRef.current);
+        fallbackTimerRef.current = null;
+      }
       if (blobUrlRef.current) {
         URL.revokeObjectURL(blobUrlRef.current);
         blobUrlRef.current = null;
@@ -105,11 +142,28 @@ export default function Speakers() {
 
   const playAt = (t: number) => {
     const audio = audioRef.current;
-    if (!audio || audioLoading) return;
+    if (!audio) return;
+    const seek = () => {
       audio.currentTime = t;
       const p = audio.play();
       if (p) p.catch(() => {});
     };
+    if (audio.readyState >= 1) {
+      seek();
+      return;
+    }
+    const done = () => {
+      audio.removeEventListener("loadeddata", done);
+      audio.removeEventListener("canplay", done);
+      seek();
+    };
+    audio.addEventListener("loadeddata", done);
+    audio.addEventListener("canplay", done);
+    window.setTimeout(() => {
+      audio.removeEventListener("loadeddata", done);
+      audio.removeEventListener("canplay", done);
+    }, 2000);
+  };
 
   const toggleSelected = (label: string) => {
     const next = new Set(selected);
@@ -190,7 +244,7 @@ export default function Speakers() {
           duration={duration}
           currentTime={currentTime}
           onSeek={playAt}
-          disabled={audioLoading || !!audioError}
+          disabled={!!audioError}
         />
       </div>
 
@@ -244,7 +298,7 @@ export default function Speakers() {
                 <button
                   key={i}
                   onClick={() => playAt(s.start)}
-                  disabled={audioLoading}
+                  disabled={!!audioError}
                   className="block text-left text-sm text-ink/60 hover:text-ink w-full truncate disabled:opacity-30 disabled:pointer-events-none"
                 >
                   ▶ {s.text}