chore: remove dead build_karaoke_text, fix stale comments

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/src/services/clip_exporter.rs

@@ -345,7 +345,7 @@ fn find_next_timestamp(text: &str, from: usize) -> Option<(String, usize)> {
 }
 
 /// A single spoken line extracted from a YouTube VTT cue.
-/// Used to build the rolling two-line subtitle display.
+/// Used to build the paged teleprompter subtitle display.
 struct SpokenLine {
     plain_text: String,
     raw_text: String,
@@ -357,8 +357,7 @@ struct SpokenLine {
 
 /// Extract a flat sequence of spoken lines from YouTube auto-generated VTT content.
 /// Skips zero-duration transition cues and extracts only the active (karaoke) line
-/// from two-line cues, ignoring the context line (which is reconstructed from the
-/// previous SpokenLine during ASS generation).
+/// from two-line cues.
 fn extract_spoken_lines(content: &str) -> Vec<SpokenLine> {
     let normalized = content.replace("\r\n", "\n");
     let blocks: Vec<&str> = normalized.split("\n\n").collect();
@@ -428,26 +427,6 @@ fn extract_spoken_lines(content: &str) -> Vec<SpokenLine> {
     lines
 }
 
-/// Build a karaoke text string with \k tags from a raw VTT line's word timings.
-fn build_karaoke_text(raw: &str, cue_start: f64, cue_end: f64) -> String {
-    let words = parse_vtt_word_timings(raw, cue_start);
-    if words.len() >= 2 {
-        let mut parts = Vec::new();
-        for (i, (word, start)) in words.iter().enumerate() {
-            let next_start = if i + 1 < words.len() {
-                words[i + 1].1
-            } else {
-                cue_end
-            };
-            let duration_cs = ((next_start - start) * 100.0).round().max(1.0) as u64;
-            parts.push(format!("{{\\k{}}}{}", duration_cs, word));
-        }
-        parts.join(" ")
-    } else {
-        strip_vtt_tags(raw)
-    }
-}
-
 /// Group spoken lines into 2-line pages for the teleprompter display.
 /// If the gap between two consecutive lines exceeds `gap_threshold` seconds,
 /// the pair is split into separate single-line pages.