A busy window no longer holds up the engine, and a run's end always arrives last
Notices are written after the engine lets go, so a busy window never stalls other work, and a run's closing update never jumps ahead.
A few notices, such as the Claude account reconnecting or a side chat closing, were written to the window while the engine still held its lock. If the window was slow to read, every other chat waited. They are now written the moment the lock is released.
The update that tells the window a run has ended now waits its turn behind anything sent just before it, so the window never sees a run finish before its last words.