The transcript scrollbox (stickyScroll+stickyStart=bottom) re-pins to the bottom
on any content-height change when the user is at the bottom (@opentui/core
ScrollBox: `if (stickyStart && !_hasManualScroll) applyStickyStart`). So expanding
a tool/thinking block scrolled the clicked header up off-screen. A
ScrollAnchorProvider (transcript owns the scrollbox ref) lets toolPart/reasoningPart
wrap their toggle so scrollTop is held constant across the height change (re-asserted
over a few frames as layout settles) — the clicked header stays put and the
expansion reveals beneath it. 85 pass.
alt-glitch
cd09aa61ef