List GitHub Checks repositories

The repositories already connected.

The repositories the MCPJam GitHub App can reach — the choices a connect has. null means the question could not be ASKED: the lookup itself failed (GitHub unreachable, or the call errored); the connected items still stand, as they need no GitHub call. An EMPTY list means it was asked and came back with nothing, which covers two situations the platform does not distinguish: the App is installed but reaches no repository, and this deployment has no App installation at all. If a connect is failing against an empty list, check the installation before assuming a permissions problem.