refactor: finetune through LLMClient interface + get_running_loop

- Add submit_finetune and get_finetune_status abstract methods to LLMClient base
- Implement both methods in ZhipuAIClient using asyncio.get_running_loop()
- Rewrite finetune_service to call llm.submit_finetune / llm.get_finetune_status
  instead of accessing llm._client directly, restoring interface encapsulation
- Replace asyncio.get_event_loop() with get_running_loop() in ZhipuAIClient._call
  and all four methods in RustFSClient (deprecated in Python 3.10+)
- Update test_finetune_service to mock the LLMClient interface methods as AsyncMocks
- Add two new tests in test_llm_client for submit_finetune and get_finetune_status

tests/test_finetune_service.py

@@ -1,8 +1,8 @@
-"""T046: Tests for finetune_service — written FIRST (TDD), must FAIL before implementation."""
-import asyncio
+"""Tests for finetune_service — uses LLMClient interface (no internal SDK access)."""
 import pytest
-from unittest.mock import MagicMock, AsyncMock, patch
+from unittest.mock import MagicMock, AsyncMock
 
+from app.clients.llm.base import LLMClient
 from app.core.exceptions import LLMCallError
 from app.models.finetune_models import (
     FinetuneStartRequest,
@@ -16,18 +16,15 @@ from app.models.finetune_models import (
 # ---------------------------------------------------------------------------
 
 def _make_llm(job_id: str = "glm-ft-test", status: str = "running", progress: int | None = None):
-    """Return a mock that looks like ZhipuAIClient with ._client.fine_tuning.jobs.*"""
-    create_resp = MagicMock()
-    create_resp.id = job_id
-
-    retrieve_resp = MagicMock()
-    retrieve_resp.status = status
-    retrieve_resp.progress = progress
-    retrieve_resp.error_message = None  # explicitly set to avoid MagicMock auto-attribute
-
-    llm = MagicMock()
-    llm._client.fine_tuning.jobs.create.return_value = create_resp
-    llm._client.fine_tuning.jobs.retrieve.return_value = retrieve_resp
+    """Return a MagicMock(spec=LLMClient) with submit_finetune and get_finetune_status as AsyncMocks."""
+    llm = MagicMock(spec=LLMClient)
+    llm.submit_finetune = AsyncMock(return_value=job_id)
+    llm.get_finetune_status = AsyncMock(return_value={
+        "job_id": job_id,
+        "status": status,
+        "progress": progress,
+        "error_message": None,
+    })
     return llm
 
 
@@ -53,7 +50,7 @@ async def test_submit_finetune_returns_job_id():
 
 
 @pytest.mark.asyncio
-async def test_submit_finetune_calls_sdk_with_correct_params():
+async def test_submit_finetune_calls_interface_with_correct_params():
     from app.services.finetune_service import submit_finetune
 
     llm = _make_llm(job_id="glm-ft-xyz")
@@ -65,16 +62,16 @@ async def test_submit_finetune_calls_sdk_with_correct_params():
 
     await submit_finetune(req, llm)
 
-    llm._client.fine_tuning.jobs.create.assert_called_once_with(
-        training_file="s3://bucket/train.jsonl",
-        model="glm-4",
-        hyperparameters={"n_epochs": 5},
+    llm.submit_finetune.assert_awaited_once_with(
+        "s3://bucket/train.jsonl",
+        "glm-4",
+        {"n_epochs": 5},
     )
 
 
 @pytest.mark.asyncio
 async def test_submit_finetune_none_hyperparams_passes_empty_dict():
-    """hyperparams=None should be passed as {} to the SDK."""
+    """hyperparams=None should be passed as {} to the interface."""
     from app.services.finetune_service import submit_finetune
 
     llm = _make_llm(job_id="glm-ft-nohp")
@@ -85,19 +82,19 @@ async def test_submit_finetune_none_hyperparams_passes_empty_dict():
 
     await submit_finetune(req, llm)
 
-    llm._client.fine_tuning.jobs.create.assert_called_once_with(
-        training_file="s3://bucket/train.jsonl",
-        model="glm-4",
-        hyperparameters={},
+    llm.submit_finetune.assert_awaited_once_with(
+        "s3://bucket/train.jsonl",
+        "glm-4",
+        {},
     )
 
 
 @pytest.mark.asyncio
-async def test_submit_finetune_raises_llm_call_error_on_sdk_failure():
+async def test_submit_finetune_raises_llm_call_error_on_failure():
     from app.services.finetune_service import submit_finetune
 
-    llm = MagicMock()
-    llm._client.fine_tuning.jobs.create.side_effect = RuntimeError("SDK exploded")
+    llm = MagicMock(spec=LLMClient)
+    llm.submit_finetune = AsyncMock(side_effect=LLMCallError("微调任务提交失败: SDK exploded"))
 
     req = FinetuneStartRequest(
         jsonl_url="s3://bucket/train.jsonl",
@@ -144,11 +141,11 @@ async def test_get_finetune_status_includes_progress():
 
 
 @pytest.mark.asyncio
-async def test_get_finetune_status_raises_llm_call_error_on_sdk_failure():
+async def test_get_finetune_status_raises_llm_call_error_on_failure():
     from app.services.finetune_service import get_finetune_status
 
-    llm = MagicMock()
-    llm._client.fine_tuning.jobs.retrieve.side_effect = RuntimeError("SDK exploded")
+    llm = MagicMock(spec=LLMClient)
+    llm.get_finetune_status = AsyncMock(side_effect=LLMCallError("查询微调任务失败: SDK exploded"))
 
     with pytest.raises(LLMCallError):
         await get_finetune_status("glm-ft-bad", llm)