refactor: clean up and refactor PR code

- Refactor duplicated video event listener boilerplate in wireVideoEvents()
  into onVideoEvent() helper (viewer.js: -57 lines)
- Fix 3 ESLint no-unused-vars warnings (bare catch instead of unused _e)
- Fix 1 additional no-unused-vars: unused 'data' param in MANIFEST_LOADED
- Remove dead 'Hls.cast' entry from playerRank map (no strategy produces it)
- Remove deprecated .eslintignore file (ESLint v9 uses flat config only)
- Add __tests__/ to ESLint ignores in flat config

Net: -20 lines (46 ins, 66 del). 83/83 tests pass, lint clean (0 warnings)

src/viewer/viewer.js

@@ -320,7 +320,7 @@ function wireHlsEvents(hls, video, panel) {
   const HlsEvents = window.Hls.Events;
 
   // --- Manifest lifecycle ---
-  hls.on(HlsEvents.MANIFEST_LOADED, (_ev, data) => {
+  hls.on(HlsEvents.MANIFEST_LOADED, () => {
     state.phase = 'loading';
     state.lastEvent = 'MANIFEST_LOADED';
     state.lastActivity = Date.now();
@@ -524,35 +524,22 @@ function wireHlsEvents(hls, video, panel) {
  * These complement hls.js events by providing browser-level playback state.
  */
 function wireVideoEvents(video) {
-  video.addEventListener('playing', () => {
-    const s = panelStates.get(video);
-    if (s) {
-      s.phase = 'playing';
-      s.lastEvent = 'video.playing';
+  // Helper: bind a video event that updates state and re-renders.
+  // Skips the handler if the panel state has already been cleaned up.
+  function onVideoEvent(eventName, updater) {
+    video.addEventListener(eventName, () => {
+      const s = panelStates.get(video);
+      if (!s) return;
+      updater(s);
       s.lastActivity = Date.now();
-      renderPanelState(video, s._panel);
-    }
-  });
+      if (s._panel) renderPanelState(video, s._panel);
+    });
+  }
 
-  video.addEventListener('waiting', () => {
-    const s = panelStates.get(video);
-    if (s) {
-      s.phase = 'buffering';
-      s.lastEvent = 'video.waiting';
-      s.lastActivity = Date.now();
-      renderPanelState(video, s._panel);
-    }
-  });
-
-  video.addEventListener('stalled', () => {
-    const s = panelStates.get(video);
-    if (s) {
-      s.phase = 'buffering';
-      s.lastEvent = 'video.stalled';
-      s.lastActivity = Date.now();
-      renderPanelState(video, s._panel);
-    }
-  });
+  // Track playback phase transitions.
+  onVideoEvent('playing', s => { s.phase = 'playing'; s.lastEvent = 'video.playing'; });
+  onVideoEvent('waiting', s => { s.phase = 'buffering'; s.lastEvent = 'video.waiting'; });
+  onVideoEvent('stalled', s => { s.phase = 'buffering'; s.lastEvent = 'video.stalled'; });
 
   // Track actual playback position (fragments are delivered out of order but
   // the browser's timeupdate fires as they are played back sequentially).
@@ -563,6 +550,7 @@ function wireVideoEvents(video) {
     s.duration = video.duration || 0;
   });
 
+  // Seek events — update activity marker, re-render.
   video.addEventListener('seeking', () => {
     const s = panelStates.get(video);
     if (s) {
@@ -571,14 +559,7 @@ function wireVideoEvents(video) {
     }
   });
 
-  video.addEventListener('seeked', () => {
-    const s = panelStates.get(video);
-    if (s) {
-      s.lastEvent = 'video.seeked';
-      s.lastActivity = Date.now();
-      renderPanelState(video, s._panel);
-    }
-  });
+  onVideoEvent('seeked', s => { s.lastEvent = 'video.seeked'; });
 }
 
 /* ======================================================================== */