The mesh gRPC link rides the module lane

The gRPC mesh transport — the endpoint Python and Node workers connect through, and the same one the React frontend uses for its live browser connection — now ships as the MeshWeaver.Hosting.Grpc module instead of being hard-wired into the portal. It stays on by default in every deployment, because the React GUI depends on it; a deployment with no React frontend and no foreign-language workers can now switch the whole surface off with one Modules:Assemblies line. Nothing changes for users: connections, tokens, and the trusted co-deployed gates work exactly as before.