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/bus.py

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+"""运行时事件总线：瀑布节点 + 可否决监听器。
+
+设计依据 docs/architecture/lingtai-runtime.md §1/§2：注入、审计、安全都在事件层做，
+不改循环骨架。监听器按注册序执行；任一监听器抛 ``Veto`` 即中断该节点（否决），
+否决事实由调用方记录（safety.ruled 等事件），总线本身不落库。
+"""
+
+from __future__ import annotations
+
+import fnmatch
+from collections import defaultdict
+from collections.abc import Awaitable, Callable
+from dataclasses import dataclass, field
+from typing import Any
+
+# 瀑布节点名（契约词典 §8.3 的可否决子集）
+NODE_RUN_REQUESTED = "run.requested"
+NODE_TURN_STARTED = "turn.started"
+NODE_LLM_PRE_REQUEST = "llm.pre_request"
+NODE_TOOL_PRE_EXECUTE = "tool.pre_execute"
+NODE_RESULT_PRE_ACCEPT = "result.pre_accept"
+
+WATERFALL_NODES = frozenset(
+    {
+        NODE_RUN_REQUESTED,
+        NODE_TURN_STARTED,
+        NODE_LLM_PRE_REQUEST,
+        NODE_TOOL_PRE_EXECUTE,
+        NODE_RESULT_PRE_ACCEPT,
+    }
+)
+
+
+class Veto(Exception):
+    """监听器否决：携带裁决摘要（reason / 规则标识）。"""
+
+    def __init__(self, reason: str, *, rule: str = "", details: dict[str, Any] | None = None):
+        super().__init__(reason)
+        self.reason = reason
+        self.rule = rule
+        self.details = details or {}
+
+
+@dataclass(frozen=True)
+class RunContext:
+    """节点监听器可见的运行上下文（只读视图，变更经事件日志）。"""
+
+    run_id: str
+    character_id: str
+    trace_id: str | None = None
+    payload: dict[str, Any] = field(default_factory=dict)
+
+
+Listener = Callable[[str, RunContext], Awaitable[None]]
+
+
+class WaterfallBus:
+    """瀑布节点订阅与触发。"""
+
+    def __init__(self) -> None:
+        self._listeners: dict[str, list[Listener]] = defaultdict(list)
+
+    def on(self, node: str, listener: Listener) -> None:
+        """注册节点监听器；支持 glob 通配（如 ``llm.*``）。"""
+        if not any(fnmatch.fnmatch(node, pattern) for pattern in WATERFALL_NODES):
+            raise ValueError(f"未知瀑布节点：{node}")
+        self._listeners[node].append(listener)
+
+    async def fire(self, node: str, context: RunContext) -> None:
+        """按注册序触发监听器；任一否决即停止后续。
+
+        精确键与通配键（如 ``llm.*``）各自成列表，列表内保持注册序；
+        两种键之间的相对顺序不保证，需要严格顺序的场景用精确注册。
+        """
+        for key, listeners in self._listeners.items():
+            if key != node and not fnmatch.fnmatch(node, key):
+                continue
+            for listener in list(listeners):
+                await listener(node, context)