[Zhoujie628]

Summary

• generalize host-owned A2A-T callback examples and keep them compilable
• expose standard A2A task-list management through the authenticated engine transport
• clean stale active demo tasks before opening independent protocol channels or starting workflows

Validation

• mvn -B clean verify
• workflow-engine: 171 tests
• spring-boot-starter: 6 tests
• samples: 85 tests

Notes

• cleanup is demo-only and fail-fast by default
• no vendor-specific Order adapter code is included in main