Mark the Document tab when the Planner writes out of view

After answering a decision in Decisions (or while in Chat on a phone), the
Planner's resumed turn rewrote the document with no sign on the Document tab.
The tab now shows a petrol dot that breathes while the turn writes and stays
still once changes wait, clearing when the document is viewed.

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