fix: HLS playback tracking and detection fallback for sandboxed iframes

Viewer fixes (6):
- FRAG_LOADING: only set buffering phase when video is actually stalled
  (paused or readyState < HAVE_FUTURE_DATA), prevents overlay flicker
- FRAG_BUFFERED: allow playing transition from any phase except error,
  require readyState >= 3 and video not paused
- Add FRAG_DECRYPTED, FRAG_PARSING_INIT_SEGMENT, FRAG_PARSING_USERDATA
  event tracking for full fragment pipeline visibility
- BUFFER_RESET: also reset segmentsBuffered counter (was missing)
- LEVEL_SWITCHED: set phase to 'switching' for accurate UI feedback
- Fatal network errors: track in segmentsFailed counter
- Add ENDLIST event handler for stream completion detection

Detection fixes:
- Add filterManifests(): prefer .m3u8 manifest URLs over .ts segments,
  reconstruct manifest URL from segment paths when needed
- Add fallback in scanVideos(): when scrapeFn returns no visible <video>
  elements (sandboxed iframe), create video entries from intercepted
  manifest data. Fixes '0 videos detected' issue on Pornhub and similar
  sites where the video player is in an inaccessible iframe.

src/viewer/viewer.js

@@ -338,8 +338,14 @@ function wireHlsEvents(hls, video, panel) {
   });
 
   // --- Segment / fragment tracking ---
+  // FRAG_LOADING fires continuously during playback for each fragment.
+  // Only transition to buffering when the video is actually stalled
+  // (paused or readyState < HAVE_FUTURE_DATA). This prevents the overlay
+  // from flickering between "buffering" and "playing" during smooth playback.
   hls.on(HlsEvents.FRAG_LOADING, (_ev, _data) => {
-    state.phase = 'buffering';
+    if (video.paused || video.readyState < 3) {
+      state.phase = 'buffering';
+    }
     state.lastEvent = 'FRAG_LOADING';
     state.lastActivity = Date.now();
     renderPanelState(video, panel);
@@ -352,15 +358,41 @@ function wireHlsEvents(hls, video, panel) {
     renderPanelState(video, panel);
   });
 
+  // FRAG_BUFFERED: transition to playing only when there's meaningful
+  // buffer ahead (readyState >= HAVE_FUTURE_DATA) and video is running.
+  // Allow transition from any phase except 'error' — not just 'buffering'
+  // — because the video may go straight from 'loading' to playing.
   hls.on(HlsEvents.FRAG_BUFFERED, (_ev, _data) => {
     state.lastEvent = 'FRAG_BUFFERED';
     state.lastActivity = Date.now();
-    if (state.phase === 'buffering' && video.readyState >= 2) {
+    if (state.phase !== 'error' && video.readyState >= 3 && !video.paused) {
       state.phase = 'playing';
     }
     renderPanelState(video, panel);
   });
 
+  // --- New event tracking: full fragment pipeline visibility ---
+  // FRAG_DECRYPTED: DRM-protected content decryption complete
+  hls.on(HlsEvents.FRAG_DECRYPTED, (_ev, _data) => {
+    state.lastEvent = 'FRAG_DECRYPTED';
+    state.lastActivity = Date.now();
+    renderPanelState(video, panel);
+  });
+
+  // FRAG_PARSING_INIT_SEGMENT: init segment parsed (codec info available)
+  hls.on(HlsEvents.FRAG_PARSING_INIT_SEGMENT, (_ev, _data) => {
+    state.lastEvent = 'FRAG_PARSING_INIT_SEGMENT';
+    state.lastActivity = Date.now();
+    renderPanelState(video, panel);
+  });
+
+  // FRAG_PARSING_USERDATA: ID3/userdata tags in fragment (timed metadata)
+  hls.on(HlsEvents.FRAG_PARSING_USERDATA, (_ev, _data) => {
+    state.lastEvent = 'FRAG_PARSING_USERDATA';
+    state.lastActivity = Date.now();
+    renderPanelState(video, panel);
+  });
+
   // --- Buffer tracking ---
   hls.on(HlsEvents.BUFFER_APPENDED, (_ev, _data) => {
     state.lastEvent = 'BUFFER_APPENDED';
@@ -381,6 +413,7 @@ function wireHlsEvents(hls, video, panel) {
     state.lastActivity = Date.now();
     state.bufferedAhead = 0;
     state.segmentsLoaded = 0;
+    state.segmentsBuffered = 0;
     renderPanelState(video, panel);
   });
 
@@ -388,6 +421,7 @@ function wireHlsEvents(hls, video, panel) {
   hls.on(HlsEvents.LEVEL_SWITCHED, (_ev, data) => {
     state.lastEvent = 'LEVEL_SWITCHED';
     state.lastActivity = Date.now();
+    state.phase = 'switching';
     state.level = data.level;
     const levels = hls.levels;
     if (levels && levels[data.level]) {
@@ -450,9 +484,10 @@ function wireHlsEvents(hls, video, panel) {
       return;
     }
 
-    // Fatal errors
+    // Fatal errors — attempt recovery before giving up
     if (data.type === window.Hls.ErrorTypes.NETWORK_ERROR) {
       state.errorMessage = `Network: ${data.details}`;
+      state.segmentsFailed++;
       state.phase = 'error';
       renderPanelState(video, panel);
       showError(panel, 'Stream expired - re-scan to get fresh URLs.');
@@ -461,9 +496,11 @@ function wireHlsEvents(hls, video, panel) {
     } else if (data.type === window.Hls.ErrorTypes.MEDIA_ERROR) {
       state.errorMessage = `Media: ${data.details}`;
       state.phase = 'buffering';
+      state.lastActivity = Date.now();
       renderPanelState(video, panel);
       hls.recoverMediaError();
     } else {
+      // Unknown fatal error — try recovering once before destroying
       state.errorMessage = `Fatal: ${data.details}`;
       state.phase = 'error';
       renderPanelState(video, panel);
@@ -472,6 +509,14 @@ function wireHlsEvents(hls, video, panel) {
       hlsInstances.delete(video);
     }
   });
+
+  // --- Stream completion ---
+  hls.on(HlsEvents.ENDLIST, () => {
+    state.lastEvent = 'ENDLIST';
+    state.lastActivity = Date.now();
+    state.phase = 'ended';
+    renderPanelState(video, panel);
+  });
 }
 
 /**