refactor: 重构推理引擎控制逻辑，修复连续批处理核心缺陷

- 修复 decode 阶段新任务覆盖已有任务的严重缺陷
- 修复线程安全问题（热路径无锁竞争）
- 修复前缀缓存引用计数管理不当导致缓存被驱逐
- 修复 pad_id 缺失导致全量 prefill 崩溃
- 修复 RoPE 位置错乱（不同位置任务共用 start_pos）
- 新增 slot 版本追踪实现前缀缓存零拷贝复用
- 新增异步流式生成接口避免阻塞事件循环
- 添加完整英文文档字符串

tests/inference/conftest.py

@@ -32,8 +32,15 @@ def mock_model_param():
 @pytest.fixture
 def mock_engine():
     """Create a mock InferenceEngine."""
+
+    async def _async_gen():
+        yield "chunk1"
+        yield "chunk2"
+        yield "[DONE]"
+
     mock = MagicMock()
     mock.generate.return_value = "mock response"
+    mock.generate_async.return_value = _async_gen()
     mock.get_stats.return_value = {
         "total_tasks": 0,
         "total_tokens": 0,

tests/inference/test_scheduler_concurrency.py

@@ -21,7 +21,7 @@ def test_prefix_cache_concurrent_insert_find():
     def insert_worker():
         try:
             for i in range(50):
-                cache.insert((i,), slot=i % 10)
+                cache.insert((i,), slot=i % 10, slot_ver=0)
                 results["inserts"] += 1
         except Exception as e:
             results["errors"].append(str(e))
@@ -29,7 +29,7 @@ def test_prefix_cache_concurrent_insert_find():
     def find_worker():
         try:
             for i in range(50):
-                cache.find_longest_prefix([i])
+                cache.find([i])
                 results["finds"] += 1
         except Exception as e:
             results["errors"].append(str(e))
@@ -53,7 +53,7 @@ def test_prefix_cache_concurrent_release():
 
     # Insert some prefixes
     for i in range(10):
-        cache.insert((i,), slot=i)
+        cache.insert((i,), slot=i, slot_ver=0)
 
     results = {"errors": []}
 
@@ -84,10 +84,10 @@ def test_prefix_cache_concurrent_insert_release_find():
         try:
             for i in range(20):
                 token_ids = (worker_id * 100 + i,)
-                cache.insert(token_ids, slot=worker_id)
+                cache.insert(token_ids, slot=worker_id, slot_ver=0)
 
                 # Find after insert
-                cache.find_longest_prefix(list(token_ids))
+                cache.find(list(token_ids))
 
                 # Release
                 cache.release(token_ids)
@@ -277,7 +277,7 @@ def test_prefix_cache_insert_same_prefix_concurrently():
     def insert_worker():
         try:
             # All workers try to insert the same prefix
-            cache.insert((1, 2, 3), slot=threading.current_thread().name)
+            cache.insert((1, 2, 3), slot=0, slot_ver=0)
             node = cache.root.children.get(1)
             if node:
                 node = node.children.get(2)
@@ -306,8 +306,7 @@ def test_prefix_cache_ref_count_underflow_prevention():
     """Test that ref_count doesn't go negative."""
     cache = PrefixCacheManager(max_capacity=100)
 
-    # Insert a prefix
-    cache.insert((1, 2, 3), slot=0)
+    cache.insert((1, 2, 3), slot=0, slot_ver=0)
 
     # Release multiple times
     for _ in range(5):

tests/inference/test_server.py

@@ -100,13 +100,12 @@ def test_chat_completions_non_stream(client, loaded_model, mock_engine, monkeypa
 def test_chat_completions_stream(client, loaded_model, mock_engine, monkeypatch):
     """POST /v1/chat/completions with stream=true returns SSE stream."""
 
-    # Simulate a streaming generator that yields cumulative responses
-    def stream_gen():
+    async def async_gen():
         yield "cumulative1"
         yield "cumulative2"
         yield "[DONE]"
 
-    mock_engine.generate.return_value = stream_gen()
+    mock_engine.generate_async.return_value = async_gen()
     monkeypatch.setattr("astrai.inference.server._engine", mock_engine)
     response = client.post(
         "/v1/chat/completions",