List the codebase functions a workflow can be pointed at.

Staff-only, like every other surface for this tool type. The shaping lives in agentic_workflow_framework.codebase_functions.introspection so this endpoint and the copilot's equivalent describe the registry identically rather than drifting.

unavailable_modules reports catalogued modules that could not be imported in this service. That is expected rather than broken when a function depends on a package this image does not carry, and it is the fastest way to tell that apart from a misspelled id.