Two faults in the crop that "Add N comments" attaches, both visible in a
two-comment batch on one page.
The marker was missing. showDraft sets the marker's style and resolves, but
resolving only means the property is set — the compositor has not drawn it.
capturePage then photographed the frame before the marker existed, so crops
arrived outlined in blue with no number, while the prompt line said "Image N
marks the target in blue". beginCapture now waits two animation frames, which
puts the shot after the paint.
The wrong marker could appear. Saved pins stay drawn on the page, so any pin
within the crop padding of the new element landed inside the shot: a comment
on a heading came back carrying the marker belonging to the comment on the
paragraph below it, pointing the agent at the wrong element. Saved pins and
hover chrome are hidden for the duration of the shot and restored after.
Restoring runs in a finally, so a capture that throws cannot leave every saved
pin invisible on the page, and the guest calls are best-effort — a torn-down
overlay degrades to the old unbracketed shot rather than failing the capture.
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