feat: make mode creation preview-only and cache-safe

tests/unit/test_vehicle_mcp_server.py

@@ -111,7 +111,7 @@ def test_initialize_and_tool_catalog_expose_only_safe_arguments() -> None:
     properties = tools[1]["inputSchema"]["properties"]
     assert set(properties) == {"request_token", "plan"}
     assert properties["plan"]["additionalProperties"] is False
-    assert properties["plan"]["properties"]["requests"]["maxItems"] == 12
+    assert properties["plan"]["properties"]["requests"]["maxItems"] == 20
     assert not {
         "approval_token",
         "hardware_access_bypass",
@@ -149,7 +149,7 @@ def test_structured_plan_is_validated_and_forwarded_without_freeform_instruction
     "plan",
     [
         {"requests": []},
-        {**_sample_plan(), "requests": _sample_plan()["requests"] * 13},
+        {**_sample_plan(), "requests": _sample_plan()["requests"] * 21},
         {
             **_sample_plan(),
             "requests": [{**_sample_plan()["requests"][0], "raw_can": "01 02 03"}],