Device log proved the residual 30-78ms end-of-slide hitch is NOT the content-layer demote
(content stays promoted) and NOT the re-render (reconcile, longtasks:[]). It's the chat-list
column flipping display:flex->none at transitionend, which reflows that whole subtree. Keep
the list RENDERED behind the conversation (position:absolute; z-index:0; covered by the opaque
content pane) instead of toggling display. Teardown now only clears transforms = no reflow.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Sravan
82d0154313
