Full remote input parity: forward mouse and structured key events over IPC

- New key_event/mouse_event client messages (crossterm serde) that run
  through the complete WM event handling on the server — remote clients
  get window focus, drag/resize and mouse forwarding into virtual
  terminals (SGR/UTF-8/X10) identical to standalone mode
- tui-wm -c now forwards mouse events; previously only keyboard worked
  remotely
- IPC unit tests + end-to-end integration test (tests/integration.py):
  daemon, frames, click/scroll SGR forwarding, popups, TUI-FM in a
  window — 12/12 passing
- Document the new messages in SOCKET_API.md

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main.rs

@@ -383,6 +383,12 @@ fn handle_ipc_event(
                         }
                     }
                 }
+                ClientMessage::KeyEvent { event } => {
+                    app.handle_event(crossterm::event::Event::Key(event));
+                }
+                ClientMessage::MouseEvent { event } => {
+                    app.handle_event(crossterm::event::Event::Mouse(event));
+                }
                 ClientMessage::Resize { width, height } => {
                     if let Some(client) = all_clients.get_mut(&client_id) {
                         client.1 = width;