site(video): captions for the two re-synthesized narration beats

The introduction's "forms on your screen" line and runtime-ui's closing line
were re-recorded after a transcription pass found a stray syllable in one and a
clipped tail in the other. Captions follow the new timings.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: claude