fix(subtitles): suppress overlay duplicates and reset ASS cleanup

- Suppress overlapping decorative karaoke and shadow layer copies
- Clear stale ASS-only fallback sanitization after source refresh failures

src/core/services/subtitle-cue-parser.test.ts

@@ -1558,17 +1558,23 @@ test('parseSubtitleCues suppresses a karaoke highlight sweep without publishing
           `Dialogue: ${layer},0:00:01.00,0:00:04.00,ED Romaji,,0,0,0,fx,{\\pos(${x},60)\\t(${index * 2},${index * 2 + 100},\\fscx120)}${fragment}`,
       ),
     ),
-    ...[40, 41].flatMap((layer) =>
-      sweepFragments.map(
-        ([fragment, x, start, end]) =>
-          `Dialogue: ${layer},${start},${end},ED Romaji2,,0,0,0,fx,{\\an5\\pos(${x},60)\\t(150,290,\\1a&HFF&)}${fragment}`,
+    ...sweepFragments.flatMap(([fragment, x, start, end]) =>
+      [
+        [40, x, 60],
+        [41, x + 4, 64],
+      ].map(
+        ([layer, copyX, copyY]) =>
+          `Dialogue: ${layer},${start},${end},ED Romaji2,,0,0,0,fx,{\\an5\\pos(${copyX},${copyY})\\t(150,290,\\1a&HFF&)}${fragment}`,
       ),
     ),
+    'Dialogue: 42,0:00:01.20,0:00:01.30,ED Romaji2,,0,0,0,fx,{\\fnWebdings\\pos(900,50)\\t(0,100,\\fscx120)}a',
+    'Dialogue: 42,0:00:04.00,0:00:04.20,ED Romaji2,,0,0,0,fx,{\\fnWebdings\\pos(900,50)\\t(0,100,\\fscx120)}z',
   ].join('\n');
 
   const cues = parseSubtitleCues(content, 'test.ass');
-  assert.equal(cues.length, 1);
+  assert.equal(cues.length, 2);
   assert.equal(cues[0]?.text.replace(/\s+/gu, ''), 'tosouomo');
+  assert.equal(cues[1]?.text, 'z');
 });
 
 test('parseSubtitleCues collapses drop-shadow layer copies offset by a few pixels', () => {

src/core/services/subtitle-cue-parser.ts

@@ -809,15 +809,21 @@ interface FragmentInterval {
   endTime: number;
 }
 
-/** Event time ranges with layer copies (same text, placement, and timing) collapsed. */
+/** Event time ranges with repeated same-text, same-time layer copies collapsed. */
 function distinctFragmentIntervals(events: readonly AnnotatedSubtitleCue[]): FragmentInterval[] {
   const intervals: FragmentInterval[] = [];
-  const seen = new Set<string>();
+  const previousEvents: AnnotatedSubtitleCue[] = [];
   for (const event of events) {
-    const anchors = [...fragmentPlacementAnchors(event)].sort().join('|');
-    const key = `${compactCueMatchText(event)}\0${anchors}\0${event.startTime}\0${event.endTime}`;
-    if (seen.has(key)) continue;
-    seen.add(key);
+    const compactText = compactCueMatchText(event);
+    const isLayerCopy = previousEvents.some(
+      (previous) =>
+        compactCueMatchText(previous) === compactText &&
+        previous.startTime === event.startTime &&
+        previous.endTime === event.endTime &&
+        isRepeatedFragmentCopy(previous, event),
+    );
+    previousEvents.push(event);
+    if (isLayerCopy) continue;
     intervals.push({ startTime: event.startTime, endTime: event.endTime });
   }
   return intervals.sort((a, b) => a.startTime - b.startTime || a.endTime - b.endTime);
@@ -1018,6 +1024,13 @@ function recoverFragmentOnlyAssLines(dialogue: AnnotatedSubtitleCue[]): Annotate
     const lineEvents = decorative.size ? events.filter((event) => !decorative.has(event)) : events;
     if (isProgressiveHighlightSweepGroup(lineEvents)) {
       lineEvents.forEach((event) => suppressed.add(event));
+      const spanStart = Math.min(...lineEvents.map((event) => event.startTime));
+      const spanEnd = Math.max(...lineEvents.map((event) => event.endTime));
+      for (const overlay of decorative) {
+        if (overlay.startTime < spanEnd && overlay.endTime > spanStart) {
+          suppressed.add(overlay);
+        }
+      }
       continue;
     }
     for (const cluster of clusterAssFragmentEvents(lineEvents)) {