fix(subtitles): recover canonical lines from ASS animation (#207)

src/renderer/subtitle-render.test.ts

@@ -1424,6 +1424,19 @@ test('subtitle annotation CSS underlines JLPT tokens without changing token colo
   );
 });
 
+test('prepareSecondarySubtitleLines drops layered duplicate lines in short stacks', () => {
+  // A word-level animation stacks one event per layer copy; the stack is too short for
+  // the karaoke heuristic but the duplicates are still never distinct content.
+  assert.deepEqual(prepareSecondarySubtitleLines('Your\\NYour\\NYour\\NYour\\Nmosaic'), [
+    'Your',
+    'mosaic',
+  ]);
+  assert.deepEqual(prepareSecondarySubtitleLines('One line\\NAnother line'), [
+    'One line',
+    'Another line',
+  ]);
+});
+
 test('prepareSecondarySubtitleLines collapses karaoke syllable spam into one deduped line', () => {
   // Karaoke-typeset OP/ED: one ASS event per syllable, duplicated across layers,
   // joined with \N by mpv's secondary-sub-text.

src/renderer/subtitle-render.ts

@@ -677,10 +677,12 @@ export function prepareSecondarySubtitleLines(text: string): string[] {
     .split('\n')
     .map((line) => line.trim())
     .filter((line) => line.length > 0);
-  if (!isKaraokeLikeLineSet(lines)) {
-    return lines;
-  }
 
+  // Identical lines in one render are layered copies of the same event (animation
+  // scripts stack several per glyph), never distinct content -- always drop them, so a
+  // short stack like "Your ×4 / mosaic" collapses without needing the karaoke
+  // heuristic. Karaoke-likeness is still judged on the raw stack, where the layered
+  // repetition is the signal.
   const seen = new Set<string>();
   const unique: string[] = [];
   for (const line of lines) {
@@ -688,6 +690,10 @@ export function prepareSecondarySubtitleLines(text: string): string[] {
     seen.add(line);
     unique.push(line);
   }
+  if (!isKaraokeLikeLineSet(lines)) {
+    return unique;
+  }
+
   return [unique.join(' ')];
 }