fix(cache): stabilize tool ordering and cache markers for MCP

tests/tools/test_tool_registry.py

@@ -0,0 +1,49 @@
+from __future__ import annotations
+
+from typing import Any
+
+from nanobot.agent.tools.base import Tool
+from nanobot.agent.tools.registry import ToolRegistry
+
+
+class _FakeTool(Tool):
+    def __init__(self, name: str):
+        self._name = name
+
+    @property
+    def name(self) -> str:
+        return self._name
+
+    @property
+    def description(self) -> str:
+        return f"{self._name} tool"
+
+    @property
+    def parameters(self) -> dict[str, Any]:
+        return {"type": "object", "properties": {}}
+
+    async def execute(self, **kwargs: Any) -> Any:
+        return kwargs
+
+
+def _tool_names(definitions: list[dict[str, Any]]) -> list[str]:
+    names: list[str] = []
+    for definition in definitions:
+        fn = definition.get("function", {})
+        names.append(fn.get("name", ""))
+    return names
+
+
+def test_get_definitions_orders_builtins_then_mcp_tools() -> None:
+    registry = ToolRegistry()
+    registry.register(_FakeTool("mcp_git_status"))
+    registry.register(_FakeTool("write_file"))
+    registry.register(_FakeTool("mcp_fs_list"))
+    registry.register(_FakeTool("read_file"))
+
+    assert _tool_names(registry.get_definitions()) == [
+        "read_file",
+        "write_file",
+        "mcp_fs_list",
+        "mcp_git_status",
+    ]