feat(agent): add tool registry domain validation

backend/src/v1/agent/tool_registry.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from typing import Any
+
+
+def validate_tool_spec(spec: dict[str, Any]) -> None:
+    name = spec["name"]
+    target = spec["execution_target"]
+    if name.startswith("ui.") and target != "frontend":
+        raise ValueError("ui.* must use frontend target")
+    if name.startswith("srv.") and target != "backend":
+        raise ValueError("srv.* must use backend target")

backend/tests/unit/v1/agent/test_tool_registry.py

@@ -0,0 +1,27 @@
+import pytest
+
+from v1.agent.tool_registry import validate_tool_spec
+
+
+class TestValidateToolSpec:
+    def test_ui_namespace_must_be_frontend(self):
+        with pytest.raises(ValueError, match="ui.* must use frontend target"):
+            validate_tool_spec(
+                {"name": "ui.navigate_to", "execution_target": "backend"}
+            )
+
+    def test_srv_namespace_must_be_backend(self):
+        with pytest.raises(ValueError, match="srv.* must use backend target"):
+            validate_tool_spec(
+                {"name": "srv.search_docs", "execution_target": "frontend"}
+            )
+
+    def test_ui_namespace_with_frontend_is_valid(self):
+        validate_tool_spec({"name": "ui.navigate_to", "execution_target": "frontend"})
+
+    def test_srv_namespace_with_backend_is_valid(self):
+        validate_tool_spec({"name": "srv.search_docs", "execution_target": "backend"})
+
+    def test_other_namespace_is_valid(self):
+        validate_tool_spec({"name": "other.tool", "execution_target": "frontend"})
+        validate_tool_spec({"name": "other.tool", "execution_target": "backend"})