feat: add comments and cleanup unused imports across codebase

static/player/subtitles/vtt.ts

@@ -1,3 +1,4 @@
+// parses VTT timestamp (mm:ss.ms or hh:mm:ss.ms) to seconds
 export const parseVttTime = (raw: string): number => {
   const parts = raw.trim().split(':');
   if (parts.length < 2) return 0;
@@ -7,15 +8,18 @@ export const parseVttTime = (raw: string): number => {
   return Number(hourPart) * 3600 + Number(minPart) * 60 + Number(secPart.replace(',', '.'));
 };
 
+// parses a single VTT cue: timestamp line + text lines
 export const parseVttCue = (line: string, lines: string[], i: number) => {
   if (!line.includes('-->')) return null;
   const [startRaw, endRaw] = line.split('-->');
   const payload: string[] = [];
   let j = i + 1;
+  // collect text until blank line
   while (j < lines.length && lines[j].trim() !== '') {
     payload.push(lines[j]);
     j++;
   }
+  // strip tags, join lines
   const text = payload
     .join('\n')
     .replace(/<[^>]+>/g, '')
@@ -24,17 +28,23 @@ export const parseVttCue = (line: string, lines: string[], i: number) => {
   return { start: parseVttTime(startRaw), end: parseVttTime(endRaw), text };
 };
 
+/**
+ * Parses full VTT file into cue array.
+ * Handles both compact (timestamp on separate line) and standard formats.
+ */
 export const parseVtt = (text: string) => {
   const lines = text.replace(/\r/g, '').split('\n');
   const cues = [];
   for (let i = 0; i < lines.length; i++) {
     const line = lines[i].trim();
     if (!line) continue;
+    // compact: cue id on line i, timestamp on i+1
     if (i + 1 < lines.length && !line.includes('-->') && lines[i + 1].includes('-->')) {
       const cue = parseVttCue(lines[i + 1].trim(), lines, i + 1);
       if (cue) cues.push(cue);
       i++;
     } else if (line.includes('-->')) {
+      // standard: timestamp on same line
       const cue = parseVttCue(line, lines, i);
       if (cue) cues.push(cue);
     }