The recorded history timeline rewrote every marker's textContent on each
render, so a scroll-triggered re-render replaced the text node under the
pointer. When that frame landed between the press and the release of a
tap, Chromium touch dropped the click and the Recorded run dialog never
opened. Text is now written only when it changes.
Adds a deterministic regression test that re-renders the timeline between
mouse down and mouse up.
Vito
b4c0189225