Add isolated Athena Deck prototype with demo control and live hardware telemetry

demo.py

@@ -0,0 +1,22 @@
+"""Owned child: health-only HTTP server, inherited bound loopback socket."""
+import json
+import socket
+import sys
+from http.server import BaseHTTPRequestHandler, HTTPServer
+
+class Handler(BaseHTTPRequestHandler):
+    def do_GET(self):
+        body = json.dumps({'service': 'athena-deck-demo', 'status': 'ok'}).encode()
+        self.send_response(200 if self.path == '/health' else 404)
+        self.send_header('Content-Type', 'application/json')
+        self.end_headers()
+        self.wfile.write(body)
+
+    def log_message(self, *args):
+        pass
+
+server = HTTPServer(('127.0.0.1', 0), Handler, bind_and_activate=False)
+server.socket.close()
+server.socket = socket.socket(fileno=int(sys.argv[1]))
+server.server_address = server.socket.getsockname()
+server.serve_forever()