feat: P1-21 ADR 变更级联失效 — 架构变更自动失效已完成任务

- TaskNode 新增 adr_refs 字段（ADR→任务溯源链）
- 新增 INVALIDATED 状态，允许覆盖 DONE/DISPATCHED
- TaskGraph.invalidate_by_adr() 级联失效 + BFS 下游传播
- PlanDelta 新增 rollback_ref（回滚快照引用）
- CascadeReport 数据结构（失效统计 + 任务ID列表）
- Eng dispatch_frozen 冻结调度，ready_tasks() 返回空
- handle_adr_invalidation() 10步处理流程（含 git revert）
- unfreeze_after_replan() Arc 重新规划后解冻
- AirRvr check_invalidated_cleanup() 检查旧代码残留
- INV-15 + L1 保障项 15 写入 SKILL.md
- 11 项功能测试全通过，含 ffmpeg→gstreamer 完整场景

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/air_runtime/task_graph.py

@@ -12,7 +12,7 @@ from typing import Any
 @dataclass
 class TaskNode:
     id: str
-    status: str = "TODO"  # TODO | DISPATCHED | DONE | BLOCKED
+    status: str = "TODO"  # TODO | DISPATCHED | DONE | BLOCKED | INVALIDATED
     task: str = ""
     files_dirs: str = ""
     done_when: str = ""
@@ -21,6 +21,7 @@ class TaskNode:
     write_set: list[str] = field(default_factory=list)
     meta: dict[str, Any] = field(default_factory=dict)
     test_required: bool = False  # P1-19.1: 边界测试强制标记
+    adr_refs: list[str] = field(default_factory=list)  # P1-21: ADR→任务溯源链
 
 
 @dataclass
@@ -36,6 +37,16 @@ class EdgeChange:
     removed: list[Edge] = field(default_factory=list)
 
 
+@dataclass
+class CascadeReport:
+    """P1-21: ADR 变更级联失效报告。"""
+    invalidated_completed: int = 0
+    terminated_in_progress: int = 0
+    cascaded_downstream: int = 0
+    rollback_ref: str = ""
+    invalidated_task_ids: list[str] = field(default_factory=list)
+
+
 @dataclass
 class PlanDelta:
     """Arc 重规划产出的增量差异，替代全量覆盖 todo.md。"""
@@ -43,6 +54,7 @@ class PlanDelta:
     added_tasks: list[TaskNode] = field(default_factory=list)
     modified_tasks: list[TaskNode] = field(default_factory=list)
     edge_changes: EdgeChange = field(default_factory=EdgeChange)
+    rollback_ref: str = ""  # P1-21: 回滚快照引用
 
 
 class TaskGraph:
@@ -51,6 +63,7 @@ class TaskGraph:
     def __init__(self):
         self.nodes: dict[str, TaskNode] = {}
         self.edges: list[Edge] = []
+        self.dispatch_frozen: bool = False  # P1-21: 调度冻结
 
     def add_node(self, node: TaskNode) -> None:
         self.nodes[node.id] = node
@@ -90,7 +103,9 @@ class TaskGraph:
                 self.nodes[edge.source].out_edges.append(edge.target)
 
     def ready_tasks(self) -> list[str]:
-        """返回当前入度为 0 且状态为 TODO 的任务。"""
+        """返回当前入度为 0 且状态为 TODO 的任务。调度冻结时返回空。"""
+        if self.dispatch_frozen:
+            return []
         return [nid for nid, n in self.nodes.items() if n.in_degree == 0 and n.status == "TODO"]
 
     def diff(self, other: TaskGraph) -> PlanDelta:
@@ -138,6 +153,7 @@ class TaskGraph:
         graph = cls()
         if not data or not isinstance(data, dict):
             return graph
+        graph.dispatch_frozen = data.get("dispatchFrozen", False)
         for nid, nd in data.get("nodes", {}).items():
             graph.nodes[nid] = TaskNode(
                 id=nd.get("id", nid),
@@ -149,6 +165,7 @@ class TaskGraph:
                 out_edges=list(nd.get("outEdges", [])),
                 write_set=list(nd.get("writeSet", [])),
                 test_required=nd.get("testRequired", False),
+                adr_refs=list(nd.get("adrRefs", [])),
             )
         for ed in data.get("edges", []):
             graph.edges.append(Edge(
@@ -205,7 +222,8 @@ class TaskGraph:
         if node.id in self.nodes:
             existing_status = self.nodes[node.id].status
             self.nodes[node.id] = node
-            if existing_status in ("DISPATCHED", "DONE"):
+            # INVALIDATED 可覆盖 DONE/DISPATCHED（P1-21: ADR 级联失效）
+            if existing_status in ("DISPATCHED", "DONE") and node.status != "INVALIDATED":
                 self.nodes[node.id].status = existing_status
 
     def _remove_edge(self, edge: Edge) -> None:
@@ -220,3 +238,70 @@ class TaskGraph:
             self.nodes[edge.target].in_degree += 1
         if edge.source in self.nodes:
             self.nodes[edge.source].out_edges.append(edge.target)
+
+    # P1-21: ADR 级联失效
+
+    def tasks_by_adr(self, adr_id: str) -> list[TaskNode]:
+        """查找所有引用指定 ADR 的任务（含已完成）。"""
+        return [n for n in self.nodes.values() if adr_id in n.adr_refs]
+
+    def _find_downstream(self, task_ids: list[str]) -> list[str]:
+        """BFS 遍历下游依赖任务。"""
+        visited: set[str] = set()
+        queue = list(task_ids)
+        while queue:
+            current = queue.pop(0)
+            if current in visited:
+                continue
+            visited.add(current)
+            node = self.nodes.get(current)
+            if node:
+                for target in node.out_edges:
+                    if target not in visited:
+                        queue.append(target)
+        # 排除起点自身
+        return [tid for tid in visited if tid not in set(task_ids)]
+
+    def invalidate_by_adr(self, adr_id: str, delta: PlanDelta) -> CascadeReport:
+        """P1-21: ADR 变更时级联失效所有相关任务。"""
+        affected = self.tasks_by_adr(adr_id)
+        completed = [t for t in affected if t.status == "DONE"]
+        in_progress = [t for t in affected if t.status == "DISPATCHED"]
+
+        # 1. 冻结调度
+        self.dispatch_frozen = True
+
+        # 2. 标记已完成任务为 INVALIDATED
+        for t in completed:
+            t.status = "INVALIDATED"
+            delta.removed_tasks.append(t.id)
+
+        # 3. 标记进行中任务为 INVALIDATED（调用方负责中止 Worker）
+        for t in in_progress:
+            t.status = "INVALIDATED"
+            delta.removed_tasks.append(t.id)
+
+        # 4. 级联失效下游
+        downstream_ids = self._find_downstream([t.id for t in completed + in_progress])
+        cascaded = []
+        for tid in downstream_ids:
+            node = self.nodes.get(tid)
+            if node and node.status in ("TODO", "DISPATCHED"):
+                node.status = "INVALIDATED"
+                delta.removed_tasks.append(tid)
+                cascaded.append(tid)
+
+        # 5. 回滚快照引用（由调用方在 git revert 后填入）
+        all_invalidated = [t.id for t in completed + in_progress] + cascaded
+
+        return CascadeReport(
+            invalidated_completed=len(completed),
+            terminated_in_progress=len(in_progress),
+            cascaded_downstream=len(cascaded),
+            rollback_ref=delta.rollback_ref,
+            invalidated_task_ids=all_invalidated,
+        )
+
+    def unfreeze_dispatch(self) -> None:
+        """P1-21: 解冻调度，在 Arc 重新生成受影响任务后调用。"""
+        self.dispatch_frozen = False