[DivyanshGarg380]

Why?

Land with an unrecognized Strategy value returned a plain error from mapper.ProtoToLandRequest. gatewayStatusError has no case for unclassified errors and returns them unchanged, so clients received codes.Unknown instead of InvalidArgument for bad input.

What?

• Wrap the strategy-mapping error in errs.NewUserError so the gateway maps it to InvalidArgument.
• Keep errors.Is(err, errUnknownStrategy) working through the wrapper (Unwrap).
• Assert the user-error classification in the mapper test, and add a gateway test that an unknown strategy yields InvalidArgument through gatewayStatusError.
• Add the matching deps to the affected BUILD.bazel files.

Test Plan

• go test ./service/submitqueue/gateway/server/mapper -count=1
• go test ./service/submitqueue/gateway/server -run TestGatewayStatusError -count=1
• python .\tool\bazel --output_user_root=C:\bazel test //service/submitqueue/gateway/server/mapper:all //service/submitqueue/gateway/server:all

Issue

Closes #996