fix(backend): 冻结 TOOLBOX 注册表为只读 MappingProxyType（CR-H7）

packages/skills/tests/test_toolbox_registry.py

@@ -7,6 +7,7 @@
 
 from __future__ import annotations
 
+import pytest
 from ww_agents import SPECS
 from ww_skills import TOOLBOX, get_tool
 
@@ -105,3 +106,11 @@ def test_get_tool_resolves_known_and_unknown() -> None:
     assert get_tool("brainstorm") is TOOLBOX["brainstorm"]
     assert get_tool("worldbuilding") is TOOLBOX["worldbuilding"]
     assert get_tool("does-not-exist") is None
+
+
+def test_toolbox_registry_is_read_only() -> None:
+    # CR-H7：注册表是单一真相源，运行时变异（注入/删除）须 fail-fast（冻结为 MappingProxyType）。
+    with pytest.raises(TypeError):
+        TOOLBOX["injected"] = TOOLBOX["brainstorm"]  # type: ignore[index]
+    with pytest.raises(TypeError):
+        del TOOLBOX["brainstorm"]  # type: ignore[attr-defined]