The open thread is marked visited several times while a reply streams.
Each mark replaced the projection's thread, so the quiet thread atom
passed it on and ChatView rendered once for the projection and once for
the shell. Visit state is read from the shell, so the thread structure
now leaves out the thread's lastVisitedAt and updatedAt, and the quiet
atom holds through a change to only those.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>