feat(demo): update cymbal-transit to Java SDK 1.0.0 and add comprehensive tests

[stenalpjolly]

Summary

Updates demo-applications/cymbal-transit to use the newly released 1.0.0 version of mcp-toolbox-sdk-java, tracks the demo in release-please-config.json, adds comprehensive unit test coverage, and resolves operational gaps in UI routing and credential resolution.

Expectation & Implementation

• Version Alignment:
  • Bumped mcp-toolbox-sdk-java version in demo-applications/cymbal-transit/pom.xml to 1.0.0 and added {x-version-update} release-please annotations.
  • Added demo-applications/cymbal-transit/pom.xml and demo-applications/cymbal-transit/README.md to release-please-config.json under extra-files for automated versioning in future releases.
  • Updated Gradle sample dependency in root README.md to 1.0.0.
• UI Web Route:
  • Added @GetMapping("/") in CymbalTransitController to return "index", ensuring the Thymeleaf web interface (templates/index.html) is rendered when accessing the root application URL.
• Resilient Identity & Error Handling:
  • Handled non-IdTokenProvider credentials gracefully in McpToolboxService.init() (such as local UserCredentials from standard ADC login) so local development does not crash with an unhandled exception.
  • Added defensive guards in McpToolboxService.bookTicket() against empty content payloads to prevent potential IndexOutOfBoundsException when the server returns validation errors.
  • Ensured externalized model configuration through GEMINI_MODEL_NAME.
• Unit Test Suite:
  • Added JUnit 5 tests covering McpToolboxService, TransitAgentTools, and TransitAgentController.
  • Configured Maven Surefire in demo-applications/cymbal-transit/pom.xml to execute **/*Test.java.

Test cases

• cloudcode.cymbal.web.McpToolboxServiceTest:
  • Verified findAllSchedules with successful response formatting, empty content, null content, and error flags.
  • Verified querySchedules parameter passing and response formatting.
  • Verified searchPolicies semantic search and query formatting.
  • Verified bookTicket parameter binding, success, and graceful failure handling without IndexOutOfBoundsException.
  • Verified init() resilient exception handling.
• cloudcode.cymbal.web.TransitAgentToolsTest:
  • Verified @Tool method delegating to McpToolboxService for findAllSchedules, querySchedules, bookTicket, and searchPolicies.
• cloudcode.cymbal.web.TransitAgentControllerTest:
  • Verified index() returns "index".
  • Verified handleUserChat() returns HTTP 200 OK with agent chat response.
  • Successfully tested full conversational flow: schedule lookup between New York and Boston, vector search for pet policy (Golden Retriever), and booking action.

Acceptance criteria

• All 20 unit tests in demo-applications/cymbal-transit pass cleanly.
• All 130 unit tests in the core SDK (mvn test -Dtest="*Test,!*E2ETest") pass cleanly.
• All modified and newly created Java files formatted with Google Java style.
• Web interface loads successfully at /.
• End-to-end chat queries against live MCP Toolbox server function properly.

Breaking changes

None.