m.replace events no longer appear as their own "* text" line — the
original row gets m.new_content and an (edited) marker. Media rows carry
a [Image]/[Video]/[Audio]/[File] prefix and the JSON export includes
mediaUrl; the UI notes attachments aren't included. Unit-tested.
Fixes#50Fixes#81
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA