refactor(conversion): body_rules 保护 cache-sensitive 字段，normalizer 保真优化与诊断日志

- RequestBuilder 新增 protected_body_keys 机制，按 provider API 格式阻止 body_rules
  改写 prompt cache 相关的顶层请求字段（messages/tools/system 等）
- Claude/Gemini normalizer 优先复用原始 raw tool_choice，避免 round-trip 丢失信息
- Claude normalizer 修复 content blocks 输出顺序（flush_text_parts），
  _coerce_claude_message_sequence 返回结构化诊断
- OpenAI normalizer 保留 raw tool call arguments 字符串与原始 tool 定义 extra 字段
- schema_utils allOf 合并保持 required 字段插入顺序
- 各转换环节增加结构化 debug 日志用于调试

tests/unit/test_handler_adapter_base.py

@@ -1,6 +1,10 @@
+from typing import Any
+
 import pytest
 
+from src.api.handlers.base.request_builder import get_cache_sensitive_protected_body_keys
 from src.api.handlers.claude.adapter import ClaudeChatAdapter
+from src.api.handlers.gemini.adapter import GeminiChatAdapter
 
 
 @pytest.mark.asyncio
@@ -23,3 +27,117 @@ def test_validate_test_base_url_trims_whitespace() -> None:
     assert ClaudeChatAdapter._validate_test_base_url("  https://api.anthropic.com/v1  ") == (
         "https://api.anthropic.com/v1"
     )
+
+
+@pytest.mark.asyncio
+async def test_claude_check_endpoint_passes_cache_sensitive_protected_keys_to_body_rules(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    from src.api.handlers.base import endpoint_checker as endpoint_checker_module
+    from src.api.handlers.base import request_builder as request_builder_module
+
+    captured: dict[str, Any] = {}
+
+    def fake_apply_body_rules(
+        body: dict[str, Any],
+        body_rules: list[dict[str, Any]],
+        protected_keys: frozenset[str] | None = None,
+        original_body: dict[str, Any] | None = None,
+    ) -> dict[str, Any]:
+        captured["body_rules"] = body_rules
+        captured["protected_keys"] = protected_keys
+        captured["original_body"] = original_body
+        return body
+
+    async def fake_run_endpoint_check(**kwargs: Any) -> dict[str, Any]:
+        captured["json_body"] = kwargs["json_body"]
+        return {"status_code": 200, "json_body": kwargs["json_body"]}
+
+    def fake_build_request_body(
+        cls: type[ClaudeChatAdapter],
+        request_data: dict[str, Any] | None = None,
+        *,
+        base_url: str | None = None,
+        provider_type: str | None = None,
+    ) -> dict[str, Any]:
+        del request_data, base_url, provider_type
+        return {
+            "messages": [{"role": "user", "content": "hello"}],
+            "system": "keep",
+        }
+
+    monkeypatch.setattr(request_builder_module, "apply_body_rules", fake_apply_body_rules)
+    monkeypatch.setattr(endpoint_checker_module, "run_endpoint_check", fake_run_endpoint_check)
+    monkeypatch.setattr(
+        ClaudeChatAdapter, "build_request_body", classmethod(fake_build_request_body)
+    )
+
+    result = await ClaudeChatAdapter.check_endpoint(
+        client=None,  # type: ignore[arg-type]
+        base_url="https://api.anthropic.com/v1",
+        api_key="test-key",
+        request_data={"model": "claude-sonnet-4-5-20250929", "stream": False},
+        body_rules=[{"action": "set", "path": "messages", "value": []}],
+    )
+
+    assert captured["protected_keys"] == get_cache_sensitive_protected_body_keys(
+        ClaudeChatAdapter.FORMAT_ID
+    )
+    assert result["status_code"] == 200
+    assert result["json_body"] == captured["json_body"]
+
+
+@pytest.mark.asyncio
+async def test_gemini_check_endpoint_passes_alias_aware_protected_keys_to_body_rules(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    from src.api.handlers.base import endpoint_checker as endpoint_checker_module
+    from src.api.handlers.base import request_builder as request_builder_module
+
+    captured: dict[str, Any] = {}
+
+    def fake_apply_body_rules(
+        body: dict[str, Any],
+        body_rules: list[dict[str, Any]],
+        protected_keys: frozenset[str] | None = None,
+        original_body: dict[str, Any] | None = None,
+    ) -> dict[str, Any]:
+        captured["body_rules"] = body_rules
+        captured["protected_keys"] = protected_keys
+        captured["original_body"] = original_body
+        return body
+
+    async def fake_run_endpoint_check(**kwargs: Any) -> dict[str, Any]:
+        captured["json_body"] = kwargs["json_body"]
+        return {"status_code": 200, "json_body": kwargs["json_body"]}
+
+    def fake_build_request_body(
+        cls: type[GeminiChatAdapter], request_data: dict[str, Any] | None = None
+    ) -> dict[str, Any]:
+        _ = cls, request_data
+        return {
+            "contents": [{"role": "user", "parts": [{"text": "hello"}]}],
+            "systemInstruction": {"parts": [{"text": "system"}]},
+            "toolConfig": {"functionCallingConfig": {"mode": "AUTO"}},
+            "generationConfig": {"temperature": 0.1},
+        }
+
+    monkeypatch.setattr(request_builder_module, "apply_body_rules", fake_apply_body_rules)
+    monkeypatch.setattr(endpoint_checker_module, "run_endpoint_check", fake_run_endpoint_check)
+    monkeypatch.setattr(
+        GeminiChatAdapter, "build_request_body", classmethod(fake_build_request_body)
+    )
+
+    result = await GeminiChatAdapter.check_endpoint(
+        client=None,  # type: ignore[arg-type]
+        base_url="https://generativelanguage.googleapis.com",
+        api_key="test-key",
+        request_data={"model": "gemini-2.5-pro", "stream": False},
+        body_rules=[{"action": "drop", "path": "toolConfig"}],
+    )
+
+    protected_keys = captured["protected_keys"]
+    assert protected_keys == get_cache_sensitive_protected_body_keys(GeminiChatAdapter.FORMAT_ID)
+    assert {"systemInstruction", "toolConfig", "generationConfig"}.issubset(protected_keys)
+    assert result["status_code"] == 200
+    assert result["json_body"] == captured["json_body"]