When the agent live card collapses to sticky mode, its height drops from
~320px to ~40px. This layout shift caused content below to jump up,
re-triggering IntersectionObserver and creating an infinite loop.
Fix: capture the card's expanded height before collapsing, then set
minHeight on a wrapper div to preserve the space. Content below stays
put, sentinel stays out of view, no oscillation.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>