fix: restore jlpt subtitle underlines

src/renderer/subtitle-render.test.ts

@@ -901,6 +901,14 @@ test('subtitle annotation CSS changes token color without overriding typography'
   for (let level = 1; level <= 5; level += 1) {
     const plainJlptBlock = extractClassBlock(cssText, `#subtitleRoot .word.word-jlpt-n${level}`);
     assert.doesNotMatch(plainJlptBlock, /(?:^|\n)\s*color\s*:/m);
+    assert.match(plainJlptBlock, /text-decoration-line:\s*underline;/);
+    assert.match(plainJlptBlock, /text-decoration-thickness:\s*2px;/);
+    assert.match(plainJlptBlock, /text-underline-offset:\s*4px;/);
+    assert.match(
+      plainJlptBlock,
+      new RegExp(`text-decoration-color:\\s*var\\(--subtitle-jlpt-n${level}-color,`),
+    );
+    assert.match(plainJlptBlock, /text-decoration-style:\s*solid;/);
 
     const block = extractClassBlock(cssText, buildJlptColorSelector(level));
     assert.ok(block.length > 0, `word-jlpt-n${level} class should exist`);