fix: normalize raw CoT reasoning content from provider_details

[Million-mo]

Problem

When using OpenAIResponsesModel with raw CoT providers (vLLM, LM Studio, litellm bridge, gpt-oss via OpenRouter), reasoning content is not displayed to users. pydantic-ai intentionally keeps ThinkingPart.content empty for these providers — raw reasoning is stored only in provider_details['raw_content'] (by design). AgentPool's protocol converters only read content/content_delta, so reasoning was silently dropped across all protocols (ACP, OpenCode, AG-UI, builtin handlers).

Closes #118

Solution

Add a centralized event normalization step in EventMapper.map_event() that intercepts ThinkingPart/ThinkingPartDelta events with empty content/content_delta and populates them from provider_details['raw_content'].

Key technique

For PartDeltaEvent, provider_details may be a callable closure (_make_raw_content_updater). Calling it with None returns {'raw_content': [delta]} — the current delta text can be extracted from raw_content[-1] without tracking accumulated state.

For PartStartEvent, provider_details is already a resolved dict (parts manager resolves callable at creation time), so raw_content is directly accessible.

Official OpenAI reasoning summaries (where content is already populated) are not modified — normalization only triggers when content/content_delta is empty/None.

Changes

• event_mapper.py: Add _normalize_thinking_event() and _extract_raw_content_text() functions. Call normalization in map_event() before returning.
• event_converter.py (ACP): delta or "\n" → delta (remove lossy fallback)
• event_processor.py (OpenCode): if not delta: → if delta is None: in _process_thinking_start and _process_thinking_delta (preserve empty strings, only skip None)
• builtin_handlers.py: if delta: → if delta is not None: for thinking delta printing

Test Results

• 22/22 unit tests passed (tests/orchestrator/test_event_mapper_thinking_normalization.py)
• ruff check — clean
• ruff format --check — clean
• mypy — clean

Acceptance Criteria

• Reasoning content from raw CoT providers is visible to all protocol converters via content/content_delta
• Official OpenAI reasoning summaries still work (content path unchanged)
• builtin_handlers.py shows reasoning text
• ACP converter no longer substitutes "\n" for empty deltas
• OpenCode converter preserves empty string deltas (only skips None)
• No regressions in existing tests

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备份迁移自 SRC-PR#119 · 作者 @Leoyzen · 创建于 2026-07-07T06:45:56Z · head=fix/normalize-raw-cot-reasoning base=develop/agentic
源状态: merged · merge_commit_sha=1a444a30e5b3cf33d1623194e5d8f6585f24fa70