feat(n7web): sync N7 scene cards and optimize runtime

tests/unit/test_start_n7web.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+import socket
+from types import SimpleNamespace
+
+import pytest
+
+from tools import start_n7web
+
+
+def test_tcp_port_probe_detects_an_existing_listener() -> None:
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as listener:
+        listener.bind(("127.0.0.1", 0))
+        listener.listen(1)
+
+        assert start_n7web._tcp_port_is_listening(  # noqa: SLF001
+            "0.0.0.0",
+            listener.getsockname()[1],
+        )
+
+
+def test_startup_rejects_a_duplicate_service_port(monkeypatch: pytest.MonkeyPatch) -> None:
+    args = SimpleNamespace(
+        host="127.0.0.1",
+        port=8000,
+        scene_bind="0.0.0.0",
+        scene_port=8090,
+    )
+    monkeypatch.setattr(
+        start_n7web,
+        "_tcp_port_is_listening",
+        lambda _host, port: port == 8000,
+    )
+
+    with pytest.raises(RuntimeError, match="stop the previous N7Web instance"):
+        start_n7web._ensure_service_ports_available(args)  # noqa: SLF001