Follow-ups from the #506 review.
The live-frame queue opened before the fetch, freezing Pane B for the
whole round trip. It now opens beside capturedAt; the request uses the
shared terminal fetch deadline and the body read a 10 s one.
A {t:'r'} refresh queued behind a pull ran its clear() after the
disconnected marker was written and wiped it, and a close during a
refresh load wrote the marker above the replay. The marker is now an
owed flag (_markerOwed) that each load settles in its own finally.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>