refactor: 拆分大型模块为 mixin/子模块结构

- cli_handler_base.py 拆分为 7 个 mixin (event/monitor/prefetch/request/sse_helpers/stream/sync)
- usage/service.py 拆分为 6 个子模块 (types/active_requests/cache_analysis/lifecycle/pricing/query/recording)
- models/database 拆分为独立模型文件 (auth/misc/model/provider/stats/usage/user)
- DUMMY_THOUGHT_SIGNATURE 常量提升到 core/api_format/conversion/constants 统一管理
- task/service.py 内联导入提升为顶层导入
- 流处理函数签名移除冗余的 http_client 参数

tests/api/handlers/base/test_antigravity_v1internal.py

@@ -80,7 +80,7 @@ def test_convert_sse_line_unwraps_before_convert_stream_chunk() -> None:
             return []
 
     with patch(
-        "src.api.handlers.base.cli_handler_base.get_format_converter_registry",
+        "src.api.handlers.base.cli_event_mixin.get_format_converter_registry",
         return_value=_DummyRegistry(),
     ):
         _lines, _events = handler._convert_sse_line(ctx, v1_line, [])
@@ -189,7 +189,6 @@ async def test_antigravity_forces_conversion_path_in_stream_with_prefetch() -> N
     ]
     byte_iter = _AsyncIter([])  # no more bytes after prefetch
     response_ctx = SimpleNamespace(__aexit__=AsyncMock(return_value=None))
-    http_client = SimpleNamespace(aclose=AsyncMock(return_value=None))
 
     with patch.object(
         handler,
@@ -198,7 +197,7 @@ async def test_antigravity_forces_conversion_path_in_stream_with_prefetch() -> N
     ) as mock_convert:
         out = []
         async for chunk in handler._create_response_stream_with_prefetch(
-            ctx, byte_iter, response_ctx, http_client, prefetched  # type: ignore[arg-type]
+            ctx, byte_iter, response_ctx, prefetched  # type: ignore[arg-type]
         ):
             out.append(chunk)
 

tests/api/handlers/base/test_stream_processor.py

@@ -84,12 +84,7 @@ def test_process_line_handles_openai_usage_chunk_followed_by_done_without_blank_
 
 
 class _DummyResponseCtx:
-    async def __aexit__(self, exc_type, exc, tb) -> None:  # noqa: ANN001
-        return None
-
-
-class _DummyHTTPClient:
-    async def aclose(self) -> None:
+    async def __aexit__(self, exc_type: type | None, exc: BaseException | None, tb: object) -> None:
         return None
 
 
@@ -115,7 +110,6 @@ async def test_create_response_stream_flushes_usage_on_remote_protocol_error() -
         ctx=ctx,
         byte_iterator=_iter_bytes_then_remote_protocol_error(),
         response_ctx=_DummyResponseCtx(),
-        http_client=_DummyHTTPClient(),  # type: ignore[arg-type]
         prefetched_chunks=[],
         start_time=None,
     ):

tests/api/handlers/base/test_stream_processor_format_conversion.py

@@ -24,7 +24,7 @@ class DummyParser(ResponseParser):
         return ""
 
 
-async def _empty_async_iter():
+async def _empty_async_iter() -> Any:
     if False:  # pragma: no cover
         yield b""
 
@@ -43,9 +43,6 @@ async def test_create_response_stream_converts_claude_to_openai() -> None:
     response_ctx = AsyncMock()
     response_ctx.__aexit__ = AsyncMock(return_value=None)
 
-    http_client = AsyncMock()
-    http_client.aclose = AsyncMock(return_value=None)
-
     message_start = {
         "type": "message_start",
         "message": {
@@ -79,7 +76,6 @@ async def test_create_response_stream_converts_claude_to_openai() -> None:
                 ctx,
                 byte_iterator=_empty_async_iter(),
                 response_ctx=response_ctx,
-                http_client=http_client,
                 prefetched_chunks=prefetched_chunks,
             )
         ]

tests/api/handlers/base/test_stream_processor_gemini_json_fallback.py

@@ -1,5 +1,5 @@
 import json
-from typing import AsyncIterator, Optional
+from typing import AsyncIterator
 
 import pytest
 
@@ -10,12 +10,7 @@ from src.core.api_format.conversion import register_default_normalizers
 
 
 class _DummyResponseCtx:
-    async def __aexit__(self, exc_type, exc, tb) -> None:  # noqa: ANN001
-        return None
-
-
-class _DummyHTTPClient:
-    async def aclose(self) -> None:
+    async def __aexit__(self, exc_type: type | None, exc: BaseException | None, tb: object) -> None:
         return None
 
 
@@ -70,7 +65,6 @@ async def test_stream_processor_converts_gemini_json_lines_without_data_prefix()
         ctx=ctx,
         byte_iterator=_iter_bytes(upstream_lines),
         response_ctx=_DummyResponseCtx(),
-        http_client=_DummyHTTPClient(),  # type: ignore[arg-type]
         prefetched_chunks=[],
         start_time=None,
     ):