The reported bug: after F, the embed's own fullscreen button is dead. Root cause
measured in Chrome — the browser's fullscreen lock sits on OUR wrapper, so
YouTube's button would need a nested request from a cross-origin frame. Handing
the lock to the iframe fixes it, but `iframe.requestFullscreen()` only resolves
from a CLICK (from a key press the promise stays pending forever, and awaiting
it spends the activation so a fallback is denied too).
So: F keeps fullscreening our wrapper (unchanged, our overlays stay visible) and
a new toolbar button hands the lock to the iframe — verified in real Chrome:
document.fullscreenElement is the IFRAME at 1920x1024, i.e. a plain YouTube
fullscreen where its own controls work.
Round-6 review findings, all fixed:
- one _rate_limiter + one _cancel_poll shared by the yt-dlp hook and run_ffmpeg
(was three hand-rolled throttles; cancel latency differed 2s vs 1s)
- stepVolume takes {delta, fallback} — two adjacent number args were silently
transposable
- volume gestures before the player is ready are honoured instead of dropped
- normalizeVolume's fallback is typed unknown (its guard was unreachable) and
applyVolume takes a number again
- the throttle tests inject a clock instead of patching global time.monotonic