Checks SRT and WebVTT subtitle files for broken or overlapping timings, numbering gaps, empty cues, reading speed above a characters-per-second limit, long or extra lines, cues that flash by or linger, unbalanced tags, and sound labels, then rewrites and retimes the problem cues and can shift the whole file. Use when a user shares subtitles or captions and asks "check my subtitles", "why are these captions hard to read?", "fix the timing", or "make these subtitles follow the guidelines".
