Addresses Copilot review on PR #31077:
- onResize now re-checks isSticky() inside the 100ms timer so manual
scrolls during the debounce window don't get snapped back to tail.
- Comment on the virtualRows cols-keying calls out the deliberate
trade-off: per-row local state (e.g. systemOpen) resets on resize so
yoga can remeasure off live geometry. The hook's scale-by-ratio path
is too approximate for mixed markdown widths.