UI event loop clones MindState on each render tick, diffs against
the previous copy, and generates status updates from changes. Mind
no longer sends UiMessage::StatusUpdate — state changes are detected
automatically by the UI.
Removes update_status from both Mind and event_loop. DMN state
changes, turn tracking, scoring status all flow through the diff.
Zero UiMessage sends from Mind's run loop for state changes.
Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>
