Python: Fix Foundry reasoning MCP compaction

[godququ5-code]

Summary

• Preserve Foundry reasoning output as text_reasoning with the provider reasoning id when reconstructing response history.
• Treat mcp_server_tool_call as a tool-call assistant item during compaction so reasoning + MCP call pairs stay atomic.
• Add focused regressions for both Foundry reasoning reconstruction paths and sliding-window MCP compaction.

Fixes #6883

Root cause

Foundry response reconstruction converted reasoning summaries into ordinary text content, dropping the reasoning id. Core compaction also only recognized function_call assistant messages as tool-call items, so an MCP call following a reasoning item could be grouped separately and survive after its reasoning prefix was excluded.

Test plan

• uv run pytest packages/core/tests/core/test_compaction.py packages/foundry_hosting/tests/test_responses.py -q
• uv run prek run --files packages/core/agent_framework/_compaction.py packages/core/tests/core/test_compaction.py packages/foundry_hosting/agent_framework_foundry_hosting/_responses.py packages/foundry_hosting/tests/test_responses.py

Note: the pytest command exits 0, but the local environment emits unrelated OpenTelemetry exporter shutdown noise against 127.0.0.1:7897 after the tests finish.

[Copilot]

Pull request overview

Fixes Python response-history reconstruction and core compaction behavior so Foundry reasoning items and subsequent MCP tool calls remain correctly paired and valid for downstream APIs (avoiding “orphaned mcp_call” 400s in multi-turn reasoning flows).

Changes:

• Preserve Foundry reasoning summaries as text_reasoning content (instead of plain text) while retaining the provider reasoning id.
• Treat mcp_server_tool_call assistant messages as tool-call items during compaction grouping so reasoning + MCP call pairs stay atomic.
• Add targeted regression tests covering both Foundry reasoning reconstruction paths and sliding-window MCP compaction grouping.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
python/packages/foundry_hosting/agent_framework_foundry_hosting/_responses.py	Reconstruct reasoning summaries as text_reasoning while preserving reasoning IDs.
python/packages/foundry_hosting/tests/test_responses.py	Adds assertions ensuring reconstructed reasoning content type and ID are preserved.
python/packages/core/agent_framework/_compaction.py	Expands tool-call detection to include MCP server tool calls for proper grouping/compaction.
python/packages/core/tests/core/test_compaction.py	Adds regression ensuring sliding-window compaction keeps reasoning + MCP calls in the same group.

[godququ5-code]

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