Relax the one-WS-per-session invariant (#5) so multiple devices mirror the
same live terminal (everyone sees output, anyone can type — tmux-style).
- types.ts: Session.attachedWs → clients Set + clientDims Map; add cwd;
SessionManager.list() + LiveSessionInfo
- session.ts: broadcast() output/exit to all clients; attachWs JOINS (no kick,
takes dims); detachWs removes one client, stamps detachedAt only when the last
leaves; setClientDims resizes PTY to the MIN cols/rows across clients
- manager.ts: join instead of kick; broadcast status; onExit drops only when a
client was attached; list() for discovery
- server.ts: GET /live-sessions; resize → per-client setClientDims; close →
detach one client; permission gate uses clients.size
- tests: rewrote session/manager tests for multi-client (join/broadcast/min-dims/
last-detach) + list(); 222 pass, tsc clean
0718b92267