fix: use binary WebSocket frames for SSH PTY output

SSH PTY output contains non-UTF-8 bytes (terminal escape sequences).
Sending as TextMessage caused WebSocket decode errors. Switch to
BinaryMessage and handle arraybuffer on the client side.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/static/index.html

@@ -72,8 +72,9 @@
         sendResize();
       };
 
+      ws.binaryType = 'arraybuffer';
       ws.onmessage = (e) => {
-        term.write(e.data);
+        term.write(new Uint8Array(e.data));
       };
 
       ws.onclose = () => {