Update Python BYO samples to AgentServer 2.1 GA

[Shiva S (Shivakishore14)]

Summary

• pin azure-ai-agentserver-core and azure-ai-agentserver-responses to 2.1.0
• pin azure-ai-agentserver-invocations to 1.1.0
• regenerate the existing portable dependency locks required by the Hosted Agent dependency policy
• apply only the compatibility migrations required by the GA SDKs: explicit resilient-task opt-in, application-owned state replacing removed task/conversation metadata, and the GA get_input_expanded import path

No unrelated direct dependency upgrades or sample behavior changes are included.

Validation

• Hosted Agent dependency-policy check with full transitive resolution
• Python compilation and Ruff undefined-name checks for the required compatibility migrations
• uv lock and portable export synchronization
• exact file parity with the validated GA update from microsoft-foundry/foundry-samples-pr#906
• public build-readiness validation passed

CI status

The repository trusted job intentionally rejects fork PRs before Azure login and live-service testing. A maintainer must promote commit 2315d00b to a same-repository branch to run the trusted live-service gate.