fix(plex): keep play state honest across a seek that restarts the session

Seeking to a spot outside the current remux window restarts the hls.js
session, which detaches/re-attaches the media and fires 'emptied' — that
silently flips the element to paused WITHOUT a 'pause' event. Because the
play flag only tracked 'play'/'pause', the button kept showing 'playing'
while the video had actually stopped, and on a slow (proxied) load the
post-manifest play() could be rejected, leaving it stuck paused until a
click on the video.

Root cause confirmed by instrumenting the media events during a seek:
emptied(paused=true) with no accompanying pause event.

Fix: resync the play flag from video.paused on the settling events
(emptied/canplay/seeked) so the button can never contradict reality;
preserve the pre-seek play/pause intent through the session restart
(loadSession takes resumePlay); and retry play once on 'canplay' so a
rejected early play() still resumes. Verified on :8080 — backward seek
(session restart), forward seek (native) and manual pause all keep the
icon in sync (0 desync samples) and resume correctly.

frontend/src/components/PlexPlayer.tsx

@@ -271,7 +271,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
 
   // --- media setup: (re)load a session for `id` at a start offset -------------------------------
   const loadSession = useCallback(
-    async (startAt: number) => {
+    async (startAt: number, resumePlay = true) => {
       const video = videoRef.current;
       if (!video) return;
       setReady(false);
@@ -301,6 +301,16 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
       const trueStart = sess.mode === "hls" && sess.start_s > 0 ? sess.start_s - HLS_SUB_LAG : sess.start_s;
       sessionStartRef.current = trueStart;
       setSessionK(trueStart);
+      // Belt-and-suspenders resume: the play() fired on MANIFEST_PARSED / loadedmetadata can be
+      // rejected when the media isn't ready yet (slow first segments over a proxy), which would leave
+      // the video paused after a seek even though the user was watching. Retry once the element can
+      // actually play. Idempotent — only acts if still paused.
+      if (resumePlay) {
+        const onCanPlay = () => {
+          if (aliveRef.current && videoRef.current?.paused) videoRef.current.play().catch(() => {});
+        };
+        video.addEventListener("canplay", onCanPlay, { once: true });
+      }
       if (hlsRef.current) {
         hlsRef.current.destroy();
         hlsRef.current = null;
@@ -313,7 +323,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
         // Subtitles are native <track>s (not muxed into the HLS), so nothing subtitle-related here.
         hls.on(Hls.Events.MANIFEST_PARSED, () => {
           setReady(true);
-          if (aliveRef.current) video.play().catch(() => {});
+          if (aliveRef.current && resumePlay) video.play().catch(() => {});
         });
         // Restore the selected audio track ONCE hls.js has parsed the renditions — doing it on
         // MANIFEST_PARSED was too early (the track list wasn't populated, so the set was dropped and
@@ -342,7 +352,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
         const onMeta = () => {
           if (sess.mode === "direct" && startAt > 0) video.currentTime = startAt;
           setReady(true);
-          if (aliveRef.current) video.play().catch(() => {});
+          if (aliveRef.current && resumePlay) video.play().catch(() => {});
           video.removeEventListener("loadedmetadata", onMeta);
         };
         video.addEventListener("loadedmetadata", onMeta);
@@ -417,13 +427,24 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
       setPlaying(false);
       patchPrefs({ wasPlaying: false });
     };
+    // A seek that restarts the hls.js session detaches/re-attaches the media, firing 'emptied' —
+    // which silently flips paused=true WITHOUT a 'pause' event, so the play/pause pair alone let the
+    // button lie (⏸ shown while actually paused). Resync the flag from reality on the settling events
+    // so the icon can never contradict the video. (Does not touch the wasPlaying pref.)
+    const syncPlaying = () => setPlaying(!video.paused);
     video.addEventListener("timeupdate", onTime);
     video.addEventListener("play", onPlay);
     video.addEventListener("pause", onPause);
+    video.addEventListener("emptied", syncPlaying);
+    video.addEventListener("canplay", syncPlaying);
+    video.addEventListener("seeked", syncPlaying);
     return () => {
       video.removeEventListener("timeupdate", onTime);
       video.removeEventListener("play", onPlay);
       video.removeEventListener("pause", onPause);
+      video.removeEventListener("emptied", syncPlaying);
+      video.removeEventListener("canplay", syncPlaying);
+      video.removeEventListener("seeked", syncPlaying);
     };
   }, [id, patchPrefs]);
 
@@ -470,14 +491,15 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
     (target: number) => {
       const video = videoRef.current;
       if (!video) return;
+      const wasPlaying = !video.paused; // preserve play/pause intent across the seek
       const dur = durationRef.current || target;
       const T = Math.max(0, Math.min(target, dur - 1));
       absRef.current = T; // reflect the target immediately so a save/beacon right after a seek is accurate
       const rel = T - sessionStartRef.current;
       if (rel >= 0 && rel <= (video.seekable.length ? video.seekable.end(0) : 0) + 0.5) {
-        video.currentTime = rel;
+        video.currentTime = rel; // native seek within the loaded region keeps playing on its own
       } else {
-        loadSession(T);
+        loadSession(T, wasPlaying); // session restart: only auto-resume if we were playing
       }
     },
     [loadSession],