Removed the `connect.NewError(connect.CodeInternal, ...)` wrapper in the
Server's MakeDir proxy handler. Previously, this wrapper was catching
specific agent errors (like CodeAlreadyExists) and casting them into
generic Code 13 (Internal) errors, stripping the gRPC metadata.
This change allows the control-plane to act as a transparent pipeline,
ensuring the API gateway can properly interpret and route specific
filesystem failures.
8d0356e372