fix(overlay): deduplicate secondary subtitle rendering (#208)

src/renderer/subtitle-render.test.ts

@@ -1424,10 +1424,11 @@ 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.
+test('prepareSecondarySubtitleLines preserves short stacks without layer metadata', () => {
   assert.deepEqual(prepareSecondarySubtitleLines('Your\\NYour\\NYour\\NYour\\Nmosaic'), [
+    'Your',
+    'Your',
+    'Your',
     'Your',
     'mosaic',
   ]);
@@ -1447,6 +1448,18 @@ test('prepareSecondarySubtitleLines collapses karaoke syllable spam into one ded
   assert.deepEqual(prepareSecondarySubtitleLines(karaoke), ['ya This no ma ups']);
 });
 
+test('prepareSecondarySubtitleLines preserves repeated short dialogue without layer metadata', () => {
+  const dialogue = ['Wait', 'Wait', 'Wait'];
+
+  assert.deepEqual(prepareSecondarySubtitleLines(dialogue.join('\\N')), dialogue);
+});
+
+test('prepareSecondarySubtitleLines preserves short simultaneous dialogue without repeats', () => {
+  const dialogue = ['Wait', 'Go!', 'No!', 'Run!'];
+
+  assert.deepEqual(prepareSecondarySubtitleLines(dialogue.join('\\N')), dialogue);
+});
+
 test('prepareSecondarySubtitleLines keeps normal dialogue lines intact', () => {
   const dialogue = ' I never expected this. \\N\\N But here we are. ';
 

src/renderer/subtitle-render.ts

@@ -677,12 +677,10 @@ 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) {
@@ -690,10 +688,6 @@ export function prepareSecondarySubtitleLines(text: string): string[] {
     seen.add(line);
     unique.push(line);
   }
-  if (!isKaraokeLikeLineSet(lines)) {
-    return unique;
-  }
-
   return [unique.join(' ')];
 }