fix(run): forward text-frame keystrokes to pty and fix ws-pty upgrade dispatch

xterm.js's onData hands the browser a plain string, and WebSocket.send(string)
always emits a TEXT frame — pty-attach.js only forwarded BINARY frames to
pty.write(), so every keystroke was silently dropped as an unparseable JSON
control message. Now any non-control text frame reaches the pty.

Deeper root cause of the terminal never accepting input at all: the /ws
WebSocketServer used the {server, path} shorthand, whose own internal
upgrade listener calls handleUpgrade() for every upgrade on the shared
http.Server and aborts with 400 on a path mismatch — killing /ws-pty/*
upgrades before the PTY server's own listener ever ran. Switched /ws to
noServer + a manual path-checked dispatch, matching /ws-pty's pattern.

server/lib/pty-attach.js

@@ -71,19 +71,31 @@ function attach(ws, runId, { cols, rows }) {
     // callback arg (newer) or via `data.binary` on some transports — this
     // helper's own tests exercise the `{binary}` option shape used above.
     const binary = typeof isBinary === "boolean" ? isBinary : !!(isBinary && isBinary.binary);
+    const text = data.toString("utf8");
     if (binary) {
-      pty.write(data.toString("utf8"));
+      pty.write(text);
       return;
     }
-    let msg;
-    try {
-      msg = JSON.parse(data.toString("utf8"));
-    } catch {
-      return;
-    }
-    if (msg && msg.type === "resize" && Number.isFinite(msg.cols) && Number.isFinite(msg.rows)) {
-      pty.resize(msg.cols, msg.rows);
+    // The browser's WebSocket API sends a JS string as a text frame, and
+    // xterm.js's onData callback hands over plain strings — so every
+    // keystroke arrives here as text, not binary. Only a JSON control frame
+    // (matched by this same prefix check the client uses for output) is
+    // NOT keystroke input; everything else must reach the pty or typing
+    // does nothing.
+    if (text.startsWith('{"type"')) {
+      let msg;
+      try {
+        msg = JSON.parse(text);
+      } catch {
+        pty.write(text);
+        return;
+      }
+      if (msg && msg.type === "resize" && Number.isFinite(msg.cols) && Number.isFinite(msg.rows)) {
+        pty.resize(msg.cols, msg.rows);
+        return;
+      }
     }
+    pty.write(text);
   });
 
   ws.on("close", () => {