[Bug] Land returns codes.Unknown instead of InvalidArgument for an unrecognized strategy #996

Description

SubmitQueueGateway.Land called with an unrecognized Strategy enum value (for example one sent by a newer client) is answered with gRPC Unknown instead of InvalidArgument. mapper.ProtoToLandRequest returns a plain fmt.Errorf, and gatewayStatusError passes unclassified errors through unchanged, so gRPC reports Unknown. Every other invalid-input error from Land is classified as a user error and surfaces as InvalidArgument.

Steps to Reproduce

1. Start the local stack (make local-submitqueue-start).
2. Call SubmitQueueGateway.Land with a configured queue, a valid change URI, and Strategy: mergestrategypb.Strategy(9999).
3. Inspect status.Code(err).

Expected Behavior

codes.InvalidArgument, consistent with the gateway's other invalid-input errors.

Actual Behavior

codes.Unknown, with the message failed to map land strategy: unknown land strategy in proto message: 9999.

Environment

• Go version: go1.27.1
• OS: Windows
• Bazel version: 8.4.1

Additional Context

resolveLandStrategy and ProtoToLandRequest are in service/submitqueue/gateway/server/mapper/land.go. errs.NewUserError already matches controller.IsInvalidRequest in gatewayStatusError, so wrapping the mapper error is enough. I have a fix ready.