feat(standalone): 新增单机模式，KILOSTAR_MODE=standalone 时去掉 Ray 依赖

通过 StandaloneProxy 适配层让 .remote() 调用在单机模式下透明降级为
asyncio 协程调用，7 个 Actor 和 workflow task 均可在纯 asyncio 环境运行，
启动快、资源占用低。分布式模式行为完全不变。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

kilostar/core/global_workflow_manager/global_workflow_manager.py

@@ -1,6 +1,6 @@
-import ray
 import asyncio
 from typing import Dict
+from kilostar.utils.standalone_proxy import actor_class
 from kilostar.utils.ray_hook import ray_actor_hook
 from kilostar.utils.logger import get_logger
 
@@ -11,7 +11,7 @@ class TraceQueues:
         self.receive: asyncio.Queue[str] = asyncio.Queue()
 
 
-@ray.remote
+@actor_class
 class GlobalWorkflowManager:
     def __init__(self):
         self._traces: Dict[str, TraceQueues] = {}