Fade change marks at full shape and expand only agent insertions

Marks now fade through registered colour properties while every attribute
stays on, so the bleed no longer snaps off; consecutive prose marks fill the
margin between them, and framed blocks are tinted rather than outlined.
Server-authored Planner and MCP updates carry a descriptive `agent` flag, and
only those expand, and only below the reader's caret. The phone chip centres
over the document, and the change list names the verified caller first.

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