fix(backend/copilot): add decompose_goal to ToolName Literal in permissions.py

The ToolName Literal must stay in sync with TOOL_REGISTRY keys. Adds
'decompose_goal' to the platform tools section to fix CI test failures.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

autogpt_platform/backend/backend/copilot/permissions.py

@@ -77,6 +77,7 @@ ToolName = Literal[
     "create_feature_request",
     "create_folder",
     "customize_agent",
+    "decompose_goal",
     "delete_folder",
     "delete_workspace_file",
     "edit_agent",