fix: align readme and examples with v0.2.1 and validate them in ci

[GregHolmes]

Summary

• update README examples to match the current 0.2.1 SDK API surface
• refresh agent examples to use the current generated agent config types
• compile examples in CI, including SageMaker-backed examples
• add a README snippet compile smoke test so docs drift is caught automatically

Details

• replace stale WebSocket example calls with the current v1WebSocket() API
• fix Listen, Speak, Agent, and SageMaker README snippets so they match current request and event types
• update the SageMaker dependency example to com.deepgram:deepgram-sagemaker:0.1.2
• remove the old agent example exclusion and add the SageMaker transport dependency for the examples source set
• add ReadmeSnippetsCompileTest to compile Java code fences from README.md

Validation

• ./gradlew test --tests com.deepgram.ReadmeSnippetsCompileTest
• ./gradlew spotlessCheck compileExamples unitTest