fix(cli): 统一 CLI handler pending usage 的 api_format 来源

CLI stream/sync mixin 中创建 pending usage 记录时，api_format 取值
来源不一致（部分用 FORMAT_ID，部分用 allowed_api_formats[0]）。
新增 primary_api_format 属性并统一使用，确保 pending 记录的格式
与实际客户端请求格式一致。

tests/api/handlers/base/test_cli_pending_usage_format.py

@@ -0,0 +1,74 @@
+from __future__ import annotations
+
+import pytest
+
+from src.api.handlers.base.cli_stream_mixin import CliStreamMixin
+from src.api.handlers.base.cli_sync_mixin import CliSyncMixin
+
+
+class _StopExecution(Exception):
+    pass
+
+
+class _DummySyncHandler(CliSyncMixin):
+    FORMAT_ID = "openai:cli"
+
+    def __init__(self) -> None:
+        self.allowed_api_formats = ["openai:compact"]
+        self.primary_api_format = "openai:compact"
+        self.pending_calls: list[dict[str, object]] = []
+
+    def extract_model_from_request(
+        self, request_body: dict[str, object], path_params: dict[str, object] | None
+    ) -> str:
+        return str(request_body.get("model") or "unknown")
+
+    def _create_pending_usage(self, **kwargs: object) -> None:
+        self.pending_calls.append(kwargs)
+        raise _StopExecution()
+
+
+class _DummyStreamHandler(CliStreamMixin):
+    FORMAT_ID = "openai:cli"
+
+    def __init__(self) -> None:
+        self.allowed_api_formats = ["openai:compact"]
+        self.primary_api_format = "openai:compact"
+        self.pending_calls: list[dict[str, object]] = []
+
+    def extract_model_from_request(
+        self, request_body: dict[str, object], path_params: dict[str, object] | None
+    ) -> str:
+        return str(request_body.get("model") or "unknown")
+
+    def _create_pending_usage(self, **kwargs: object) -> None:
+        self.pending_calls.append(kwargs)
+        raise _StopExecution()
+
+
+@pytest.mark.asyncio
+async def test_sync_pending_usage_uses_primary_api_format() -> None:
+    handler = _DummySyncHandler()
+
+    with pytest.raises(_StopExecution):
+        await handler.process_sync(  # type: ignore[misc]
+            original_request_body={"model": "gpt-5.3-codex"},
+            original_headers={},
+        )
+
+    assert handler.pending_calls
+    assert handler.pending_calls[0]["api_format"] == "openai:compact"
+
+
+@pytest.mark.asyncio
+async def test_stream_pending_usage_uses_primary_api_format() -> None:
+    handler = _DummyStreamHandler()
+
+    with pytest.raises(_StopExecution):
+        await handler.process_stream(  # type: ignore[misc]
+            original_request_body={"model": "gpt-5.3-codex"},
+            original_headers={},
+        )
+
+    assert handler.pending_calls
+    assert handler.pending_calls[0]["api_format"] == "openai:compact"