Sender can edit their own text messages: a pencil action on the bubble loads the text into the
composer in an 'Editing' mode; saving updates the body, marks it 'edited', and pushes the change
live to the other side/tabs (chat-edited, mirroring delete). Adds messages.edited_at + editBody().
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>