Long user prompts stick to the top of the thread while the response streams
beneath them, so a multi-line prompt could eat most of the viewport. Clamp the
read-only human bubble's text to ~2 lines with a soft bottom fade; the clamp
lifts on hover or keyboard focus, and clicking the bubble still opens the edit
composer (which shows the full text). Short messages are untouched — no clamp,
no fade.
Overflow is measured on an unclamped inner wrapper so the ResizeObserver only
fires on real content/width changes, not every frame while the outer
max-height animates open; the measured height feeds --human-msg-full so
expand/collapse animate to the true height instead of overshooting the cap.
9bdf01852a