Python: Hosted Responses lose CostControl budget failure metadata

When a Foundry-hosted Agent Framework Responses agent receives a streaming model failure caused by a CostControl budget block, the raw model response includes `x-ms-budget-cause: budget_exceeded` and related budget headers. The OpenAI streaming SDK later raises a generic `APIError` from the SSE error event, and the hosting adapter currently emits a generic `response.failed` with `error.code: server_error`.

Expected behavior:
- Preserve the allowlisted CostControl response headers across the streaming exception boundary.
- Emit `response.failed.error.code` as `budget_exceeded`.
- Include compact CostControl details in response metadata so streaming and non-streaming Responses clients can render the correct budget-block experience.

The outer Responses HTTP status should remain protocol-compatible; this issue concerns the terminal failure body and metadata.