fix: handle ThinkingPart in OpenCode and OpenAI API converters (#174)

[Million-mo]

Summary

Fixes #174

ThinkingPart (LLM reasoning content) was silently dropped in two protocol server areas:

1. OpenCode server — session restore via chat_message_to_opencode() had no case for ThinkingPart; opencode_to_chat_message() had no case for ReasoningPart
2. OpenAI API server — all paths (streaming, non-streaming, responses) ignored thinking content; OpenAIMessage lacked reasoning_content field

Changes

OpenCode converters (converters.py + message.py)

• chat_message_to_opencode(): Add ThinkingPart case in pydantic match/case AND dict path (part_kind == thinking), creating ReasoningPart with metadata preserving id/provider_name/signature/provider_details
• opencode_to_chat_message(): Add ReasoningPart case restoring full ThinkingPart fields from metadata
• MessageWithParts: Add add_reasoning_part() method following existing pattern

OpenAI API server (4 files)

• completions/models.py: Add reasoning_content field to OpenAIMessage
• completions/helpers.py: Add ThinkingPartDelta match arm in stream_response() emitting reasoning_content delta
• server.py: Extract ThinkingPart content from messages in non-streaming path
• responses/helpers.py + models.py: Add ResponseReasoning output type and include reasoning in responses API

Test Plan

• 4 new tests in test_converters_thinking.py (ThinkingPart to ReasoningPart, empty skip, ReasoningPart to ThinkingPart with/without metadata)
• All 735 existing server + session tests pass (1 skipped)
• ruff check + format pass
• mypy passes on all changed files

Relationship to #155 and #156

• [PR #92] fix(orchestrator): fix Core tests failure in PR #88 #155 (PR fix: restore persisted sessions from store in list_sessions #220): Ensures ThinkingPart.content has value in message_history
• refactor: Thin-wrapper refactor — pdai Capability-first architecture (#74) #156 (PR fix(orchestrator): prevent double cancel() from killing start() generator #222): Ensures ThinkingPart metadata survives storage round-trip
• This PR ([PR #117] fix: resolve flaky test_nested_subagents_create_recursive_toolparts #174): Ensures protocol converters handle ThinkingPart/ReasoningPart

Three independent fixes covering the full chain. No overlap in changed files.

备份迁移自 SRC-PR#223 · 作者 @Million-mo · 创建于 2026-07-20T01:37:24Z · head=fix/issue-174-thinkingpart-protocol-converters base=develop/agentic
源状态: closed · merge_commit_sha=3d4a4e3b087ea726ea7444b0126bb3af29f58830

[Million-mo]

评论 by @Million-mo 于 2026-07-20T01:51:57Z（备份迁移）

Closing as duplicate — the core issue (#174, ThinkingPart silently dropped) was already fixed by #176 and merged into main.

This PR additionally preserved id/provider_name/signature/provider_details metadata during conversion, but that overlaps with the scope of #156 (tracked in PR #222). The metadata preservation fix will be delivered via #222 instead.