feat: P1-21 补充 — ADRWatcher 自动检测 + PartialReplanner 局部重规划

- 新增 adr_watcher.py: SHA256 hash 监控 ADR 文件变更
  - snapshot() 初始快照, detect_changes() 增量检测
  - 识别 new/modified/superseded/deleted 四种变更类型
  - _parse_status() 解析 ADR Status 字段
- 新增 partial_replanner.py: 局部重规划器
  - replan() 仅生成受影响任务的替代计划
  - _extract_stable_interfaces() 提取未受影响 DONE 任务接口约束
  - 产出 replan-request.json 供 Arc 读取
- Eng monitor_engine 集成 ADR 检测: 每轮轮询调用 _detect_adr_changes()
- Eng handle_adr_invalidation 集成 PartialReplanner 输出
- events.py 新增 ADR 变更相关事件常量
- task_graph.py apply_full_replace 保留 DISPATCHED, 不保留 INVALIDATED
- 10 项补充测试全通过，含完整 ADR 流程场景

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

lib/air_runtime/modes/eng_mode.py

@@ -308,6 +308,32 @@ def dispatch_worker_group(project_root: Path, group_name: str = "") -> dict:
     return result
 
 
+def _detect_adr_changes(project_root: Path, state: dict) -> list:
+    """P1-21: 检查 ADR 文件变更，返回需要级联失效的变更列表。"""
+    from air_runtime.adr_watcher import ADRWatcher, ADRChange
+    adr_dir = project_root / "AirPlan" / "docs" / "architecture" / "adr"
+    if not adr_dir.exists():
+        return []
+
+    watcher = ADRWatcher(adr_dir)
+    # 从引擎状态恢复已知 hash
+    known = state.get("adrWatcherHashes", {})
+    watcher._known_hashes = known
+
+    # 首次无 snapshot → 先初始化
+    if not known:
+        watcher.snapshot()
+        state["adrWatcherHashes"] = dict(watcher._known_hashes)
+        return []
+
+    changes = watcher.detect_changes()
+    # 持久化更新后的 hash
+    state["adrWatcherHashes"] = dict(watcher._known_hashes)
+
+    # 只返回需要级联失效的变更
+    return [c for c in changes if c.kind in ("superseded", "modified")]
+
+
 def monitor_engine(project_root: Path) -> dict:
     """L1 代码级轮询：硬编码循环检测 Worker 状态，不依赖 LLM 自觉。"""
     paths = _paths(project_root)
@@ -350,6 +376,21 @@ def monitor_engine(project_root: Path) -> dict:
     except OSError:
         resource_pressure = False
 
+    # P1-21: ADR 变更自动检测
+    adr_changes = _detect_adr_changes(project_root, state)
+    if adr_changes:
+        for change in adr_changes:
+            if change.kind in ("superseded", "modified"):
+                interventions.append({
+                    "adrId": change.adr_id,
+                    "reason": f"adr-{change.kind}",
+                    "action": "invalidate-by-adr",
+                })
+                log = EventLog(event_log_path(project_root))
+                log.emit("adr.change.detected", {
+                    "adrId": change.adr_id, "kind": change.kind,
+                })
+
     # 新增：检查 pending worktree merges — merge 失败自动升级到 AirDbg
     wt_root = project_root / ".git" / "worktrees"
     if wt_root.exists():
@@ -616,6 +657,13 @@ def handle_adr_invalidation(project_root: Path, adr_id: str) -> dict:
     # 6: git revert 已合并的旧代码（按 task_id 查找对应 commit）
     revert_results = _git_revert_invalidated(project_root, report.invalidated_task_ids)
 
+    # 6.5: 生成局部重规划请求（PartialReplanner）
+    from air_runtime.partial_replanner import PartialReplanner
+    replanner = PartialReplanner()
+    partial_delta = replanner.replan(graph, report.invalidated_task_ids)
+    replan_request_path = paths["plan_dir"] / f"replan-request-{session_stamp()}.json"
+    atomic_json_write(replan_request_path, partial_delta.replan_request)
+
     # 7: 写回更新后的 task-graph.json
     from air_runtime.modes.arc_mode import _export_task_graph_json
     _export_task_graph_json(graph, tg_json)
@@ -641,6 +689,7 @@ def handle_adr_invalidation(project_root: Path, adr_id: str) -> dict:
         },
         "terminatedWorkers": terminated_workers,
         "revertResults": revert_results,
+        "replanRequestPath": str(replan_request_path),
         "nextStep": "arc-replan-then-unfreeze",
     }