Add Bubble Tea TUI (cmd/tui) with three-pane layout

- Connects to a running daemon's IPC port on startup
- Sends join_network then get_state; listens for events in real time
- Three-pane layout: room list (left), message history (centre), peers (right)
- Tab/Shift+Tab to switch rooms, Enter to send, PgUp/PgDn to scroll
- DM rooms appear automatically when a DM arrives
- test-tui.sh boots the full stack (anchor + 3 peers) and opens the TUI
  as alice, with bob and charlie sending periodic messages as live noise
- README: layout diagram, key bindings, TUI section; roadmap item marked done

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -10,3 +10,4 @@
 .env
 .DS_Store
 *.swp
+tui