Cursor Agent8/13/2026, 8:54:12 PM

Derive one semantic user-message model for rendering, clipboard, and
accessibility so attachment-only and Canvas turns keep user authorship,
copy never leaks persistence markup, and clipboard failure is retryable.

Fixes mweinbach/agent-coworker#247

Co-authored-by: Max Weinbach <mweinbach@users.noreply.github.com>

Parentfa5c0f6