M0：灵台 Kernel 骨架（事件溯源/命台席位/瀑布总线/插件注册）与神识客户端边界，新增 POST /runs 占位闭环与测试，Alembic 基线合并为单一起点

backend/app/runtime/__init__.py

@@ -0,0 +1,16 @@
+"""灵台插件化运行时（事件总线 / 插件 / Profile）。Kernel 见 ``app.kernel``。"""
+
+from app.runtime.bus import RunContext, Veto, WaterfallBus
+from app.runtime.plugin import Plugin, PluginRegistry
+from app.runtime.profile import Profile, ProfileLayer, resolve_profile
+
+__all__ = [
+    "Plugin",
+    "PluginRegistry",
+    "Profile",
+    "ProfileLayer",
+    "RunContext",
+    "Veto",
+    "WaterfallBus",
+    "resolve_profile",
+]