enforce fixed hub destination namespace

tests/test_cli.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from rrcd.cli import _build_arg_parser, _write_default_config
+from rrcd.constants import HUB_DEST_NAME
+
+
+def test_arg_parser_rejects_dest_name_override() -> None:
+    parser = _build_arg_parser()
+
+    with pytest.raises(SystemExit):
+        parser.parse_args(["--dest-name", "custom.hub"])
+
+
+def test_default_config_does_not_emit_dest_name_field(tmp_path: Path) -> None:
+    config_path = tmp_path / "rrcd.toml"
+    identity_path = tmp_path / "hub_identity"
+
+    _write_default_config(str(config_path), str(identity_path))
+
+    content = config_path.read_text(encoding="utf-8")
+    assert "dest_name =" not in content
+    assert f"Hubs always announce on {HUB_DEST_NAME!r}." in content