Issue #49: add cross-language smoke matrix

docs/GatewayTesting.md

@@ -76,6 +76,13 @@ stdout/stderr lines emitted during the run.
 
 ## Focused Commands
 
+Run the cross-language smoke matrix tests after changing the documented client
+smoke command list:
+
+```bash
+dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj --filter FullyQualifiedName~CrossLanguageSmokeMatrixTests
+```
+
 Run the parity fixture matrix tests after changing the integration parity
 scenario list:
 
@@ -102,6 +109,7 @@ dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj
 
 ## Related Documentation
 
+- [Cross-Language Smoke Matrix](./CrossLanguageSmokeMatrix.md)
 - [Parity Fixture Matrix](./ParityFixtureMatrix.md)
 - [Gateway Process Design](./gateway-process-design.md)
 - [Worker Frame Protocol](./WorkerFrameProtocol.md)