fix(agor-pty): implement real PTY resize (TIOCSWINSZ via portable-pty)

Was only updating cached dimensions without calling PTY resize.
Shell thought terminal was wrong size → double prompts, escape code leaks.

- Session stores master PTY handle (Arc<Mutex<Box<dyn MasterPty>>>)
- resize() calls master.resize(PtySize) → issues TIOCSWINSZ
- Reader task no longer owns master handle (uses cloned reader only)

agor-pty/src/daemon.rs

@@ -314,7 +314,9 @@ async fn handle_message(
             let mut st = state.lock().await;
             match st.sessions.get_mut(&session_id) {
                 Some(sess) => {
-                    sess.note_resize(cols, rows);
+                    if let Err(e) = sess.resize(cols, rows).await {
+                        log::warn!("resize {session_id}: {e}");
+                    }
                 }
                 None => {
                     let _ = out_tx.try_send(DaemonMessage::Error {