AirPlan V2 initial release — unified scheduler with 12 sub-modes

Merges 8 V1 plugins into 1 unified plugin, adds 4 new components (dep, tst, sec, rvr).
12 sub-modes: arc, eng, do, dbg, xdb, sdb, ndb, ctx, dep, tst, sec, rvr.
L1 code-level guarantees: atomic writes, file locks, evidence gating, forced debug routing,
3-phase arc gate, evidence-first debug gate, Chinese language lock, scheduler boundary.

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

lib/air_runtime/io.py

@@ -0,0 +1,53 @@
+"""
+原子 I/O 模块 — 消除 V1 5 份 _json_dump/_json_load 重复。
+每次写入使用 tempfile + os.replace() 保证原子性，写入前自动备份。
+"""
+
+from __future__ import annotations
+
+import contextlib
+import json
+import logging
+import os
+import tempfile
+from pathlib import Path
+
+logger = logging.getLogger(__name__)
+
+
+def atomic_json_write(path: Path, data: dict | list, indent: int = 2) -> None:
+    """POSIX 原子写入：tempfile + os.replace()。写入前自动备份旧文件为 .bak（单级轮转）。"""
+    path.parent.mkdir(parents=True, exist_ok=True)
+
+    # 备份旧文件
+    if path.exists():
+        bak = path.with_suffix(path.suffix + ".bak")
+        try:
+            os.replace(str(path), str(bak))
+        except OSError as exc:
+            logger.warning("backup %s -> %s failed: %s", path, bak, exc)
+
+    fd, tmp = tempfile.mkstemp(dir=path.parent, suffix=".tmp")
+    try:
+        os.write(fd, json.dumps(data, indent=indent, ensure_ascii=False).encode("utf-8"))
+        os.close(fd)
+        os.replace(tmp, path)
+    except BaseException:
+        with contextlib.suppress(OSError):
+            os.unlink(tmp)
+        raise
+
+
+def safe_json_load(path: Path) -> dict | list | None:
+    """安全加载：处理损坏文件，自动从 .bak 恢复。文件不存在返回 None。"""
+    try:
+        return json.loads(path.read_text("utf-8"))
+    except FileNotFoundError:
+        return None
+    except (json.JSONDecodeError, UnicodeDecodeError):
+        bak = path.with_suffix(path.suffix + ".bak")
+        if bak.exists():
+            logger.warning("corrupt %s, restoring from %s", path, bak)
+            return json.loads(bak.read_text("utf-8"))
+        logger.error("corrupt %s with no backup", path)
+        return None