feat: 3.2.17中途变更处理(git驱动) + 3.2.9a Worker git强制 + 3.2.5 Phase7 squash merge + Arc git初始化检测

- 新增 ChangeClassifier（爆炸半径分类：IMPLEMENTATION/INTERFACE/GLOBAL_CONSTRAINT）
- 新增 ImpactPropagator（BFS影响传播：IMPACTED/BOUNDARY/SAFE差异化标记）
- task_graph.py：invalidate_by_adr()差异化失效 + CascadeReport扩展字段（向后兼容）
- eng_mode.py：三阶段差异化流程（分类→传播→失效→git操作→验证任务→重规划）
- eng_mode.py：_git_squash_merge_and_tag() + Phase 7 集成
- do_mode.py：_ensure_all_committed() Worker git操作强制
- adr_watcher.py：内容快照 + get_content_for_classification()
- events.py：ADR_CLASSIFIED/IMPACT_PROPAGATED/BOUNDARY_VERIFICATION_GENERATED
- partial_replanner.py：replan_with_constraints() + generate_verification_tasks()
- project_bootstrap.py：ensure_git_initialized() Arc规划前检测
- test_p1_21_phase2.py：21个新测试，95个全量测试0失败

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

lib/air_runtime/adr_watcher.py

@@ -15,10 +15,11 @@ from pathlib import Path
 class ADRChange:
     """ADR 文件变更记录。"""
     adr_id: str
-    kind: str  # "new" | "superseded" | "modified"
+    kind: str  # "new" | "superseded" | "modified" | "deleted"
     path: str = ""
     old_hash: str = ""
     new_hash: str = ""
+    old_content: str | None = None  # 3.2.17: 变更前内容，供 ChangeClassifier 分类
 
 
 class ADRWatcher:
@@ -31,16 +32,17 @@ class ADRWatcher:
     def __init__(self, adr_dir: Path):
         self._adr_dir = adr_dir
         self._known_hashes: dict[str, str] = {}
+        self._content_snapshots: dict[str, str] = {}  # 3.2.17: 内容快照供 ChangeClassifier 使用
 
     def snapshot(self) -> None:
-        """启动时记录所有 ADR 的内容 hash。"""
+        """启动时记录所有 ADR 的内容 hash 和内容快照。"""
         if not self._adr_dir.exists():
             return
         for adr_file in sorted(self._adr_dir.glob("ADR-*.md")):
             adr_id = self._extract_adr_id(adr_file)
-            self._known_hashes[adr_id] = hashlib.sha256(
-                adr_file.read_bytes()
-            ).hexdigest()
+            raw = adr_file.read_bytes()
+            self._known_hashes[adr_id] = hashlib.sha256(raw).hexdigest()
+            self._content_snapshots[adr_id] = adr_file.read_text(encoding="utf-8")
 
     def detect_changes(self) -> list[ADRChange]:
         """对比当前 ADR hash 与已知 hash，返回变更列表。"""
@@ -57,35 +59,56 @@ class ADRWatcher:
             old_hash = self._known_hashes.get(adr_id)
 
             if old_hash is None:
+                content = adr_file.read_text(encoding="utf-8")
                 changes.append(ADRChange(
                     adr_id=adr_id, kind="new",
                     path=str(adr_file), old_hash="", new_hash=current_hash,
                 ))
+                self._content_snapshots[adr_id] = content
             elif current_hash != old_hash:
+                old_content = self._content_snapshots.get(adr_id)
+                new_content = adr_file.read_text(encoding="utf-8")
                 status = self._parse_status(adr_file)
-                if status == "superseded":
-                    changes.append(ADRChange(
-                        adr_id=adr_id, kind="superseded",
-                        path=str(adr_file), old_hash=old_hash, new_hash=current_hash,
-                    ))
-                else:
-                    changes.append(ADRChange(
-                        adr_id=adr_id, kind="modified",
-                        path=str(adr_file), old_hash=old_hash, new_hash=current_hash,
-                    ))
+                kind = "superseded" if status == "superseded" else "modified"
+                changes.append(ADRChange(
+                    adr_id=adr_id, kind=kind,
+                    path=str(adr_file), old_hash=old_hash, new_hash=current_hash,
+                    old_content=old_content,
+                ))
+                self._content_snapshots[adr_id] = new_content
             self._known_hashes[adr_id] = current_hash
 
         # 检查被删除的 ADR
         for adr_id in list(self._known_hashes.keys()):
             if adr_id not in seen_ids:
+                old_content = self._content_snapshots.get(adr_id)
                 changes.append(ADRChange(
                     adr_id=adr_id, kind="deleted",
                     path="", old_hash=self._known_hashes[adr_id], new_hash="",
+                    old_content=old_content,
                 ))
                 del self._known_hashes[adr_id]
 
         return changes
 
+    def get_content_for_classification(self, change: ADRChange) -> tuple[str | None, str | None]:
+        """3.2.17: 获取 ADR 变更的旧/新内容，供 ChangeClassifier 爆炸半径分类。
+
+        返回 (old_content, new_content):
+        - modified/superseded/deleted: old=change.old_content, new=从磁盘读取
+        - new: old=None, new=从磁盘读取
+        """
+        if change.kind == "deleted":
+            return (change.old_content, None)
+        if change.kind == "new":
+            new_path = Path(change.path) if change.path else None
+            new_content = new_path.read_text(encoding="utf-8") if new_path and new_path.exists() else None
+            return (None, new_content)
+        # modified / superseded: old_content already captured in change object
+        new_path = Path(change.path) if change.path else None
+        new_content = new_path.read_text(encoding="utf-8") if new_path and new_path.exists() else None
+        return (change.old_content, new_content)
+
     @staticmethod
     def _extract_adr_id(adr_file: Path) -> str:
         """从文件名提取 ADR ID，如 'ADR-0005-ffmpeg-decode.md' → 'ADR-0005'。"""