test: register setup_mcp in the desktop_ui toolset + post-hook contracts

The toolset inventory and the post-hook ownership contract both
enumerate the GUI tools; the new tool joins both lists (and the
emit-once parametrization actually exercises its executor path).

tests/run_agent/test_run_agent.py

@@ -2285,6 +2285,7 @@ class TestAgentRuntimePostHookOwnershipSync:
         ("read_terminal", {}),
         ("read_preview", {}),
         ("read_window_below", {}),
+        ("setup_mcp", {"server": "linear", "action": "install"}),
         ("delegate_task", {"goal": "Check the child path"}),
     )
 

tests/tui_gateway/test_gui_surface_toolsets.py

@@ -25,6 +25,7 @@ GUI_TOOLS = {
     "read_terminal",
     "read_window_below",
     "react_to_message",
+    "setup_mcp",
 }