clawmates-node --selftest + server terminal tracing (diagnose blank terminal)

- Daemon: factor the terminal command into terminal_command(); add `--selftest`
  which opens the host terminal PTY locally and prints ~2.5s of raw output, so
  you can confirm tmux/zsh actually draws on a given node without the browser.
  (Verified locally: tmux spawns zsh + draws its status bar.)
- cm-api: temporary [fleet-term] eprintln tracing in open_terminal, the pty_out
  router, and the browser bridge (byte counts + sink presence) to locate where
  output stops between daemon→server→browser. To be removed once diagnosed.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

crates/cm-api/src/routes/nodes.rs

@@ -212,15 +212,21 @@ struct TermCtrl {
 
 async fn bridge_terminal(hub: Arc<NodeHub>, node_id: NodeId, socket: WebSocket) {
     let Some((sid, mut rx)) = hub.open_terminal(node_id, 80, 24).await else {
+        eprintln!("[fleet-term] bridge: open_terminal None (node offline?) node={node_id}");
         return;
     };
+    eprintln!("[fleet-term] bridge start node={node_id} sid={sid}");
     let (mut ws_tx, mut ws_rx) = socket.split();
     let to_browser = async {
+        let mut sent = 0usize;
         while let Some(bytes) = rx.recv().await {
+            sent += bytes.len();
             if ws_tx.send(Message::Binary(bytes.into())).await.is_err() {
+                eprintln!("[fleet-term] bridge: browser send failed after {sent} bytes");
                 break;
             }
         }
+        eprintln!("[fleet-term] bridge to_browser ended, {sent} bytes total");
     };
     let to_node = async {
         while let Some(Ok(msg)) = ws_rx.next().await {