Python: Python : checkpoint restore +pending request deserialization failure when hosting workflow as agent with ResponsesHostserver in foundry

@TaoChenOSU is already working on this.

Since Aug 11, 2026.

## Scenario

This occurs when a workflow is hosted as an agent via ResponseHostServer (Response protocol), aand the workflow is resumed across requests using `previous_response_id`

## when it happened
- During the hosted-agent execution (work-as-agent ), sfter a prior turn produced `request_info` and pending requests.
- on the next `/responses` call with `previous_response_id ` + `function_call_output`, the server restored checkpoint state and failed on deserializing a pending request type.

## observed behaviour

- checkpoint decode warning:
`checkpoint deserialization blocked for type 'agent_framework_orchestrations._handoff:HandoffAgentUserRequest'`
checkpoint deserialization blocked for type agent_framework_orchestrations._magentic:MagenticPlanReviewRequest

- Restore proceeded from an older/other checkpoint state
- Follow-up response was rejected
- `ValueError :Response provided for unknown request Id :

## Expected
When hosting workflow as agent:
-pending request checkpoint state should restore reliably across turns

Package versions:
agent-framework-core==1.13.0
agent-framework-foundry-hosting==1.0.0.b260730