code-to10 v6 A7: unify row_get on peer_messages

- peer_messages.row_get gains default=None (was None-only); the
  three old variants agree on all real row types (None / dict /
  sqlite3.Row): auto_memory's old default was already None, and
  lifecycle's old None special-case and dict .get give identical
  results on those types, so no call-site behavior changes and no
  call site passes a non-None default.
- auto_memory and lifecycle delete their private _row_get copies
  and import peer_messages.row_get as _row_get (precedent: server,
  worker, handler_project, handler_support already do this);
  peer_messages imports no cloud modules, so no import cycle.
  lifecycle's old broad-Exception catch differs only for pathological
  __getitem__ inputs, which are not DB rows and are out of contract;
  this is documented on row_get, not left as a second story.
- Scope note: other modules' own row_get copies (approvals,
  automations, marker_tools, todos, wait_ops) are out of this item's
  stated scope and are untouched.
- Also drops auto_memory's unused 'import os' (pre-existing F401),
  so touched files are ruff E,F clean.
- Tests: cloud/tests/test_row_get_unified.py locks the identity
  (both aliases ARE row_get), the real-row-type matrix, the
  None-default fallback, and snapshot_to_dict via the unified path.

(cherry picked from commit 1644a0b837bfefb13cdc3c93d87fc1b246026607)

cloud/tests/test_row_get_unified.py

@@ -0,0 +1,92 @@
+"""row_get 簇统一单测（A7）：三处走同一函数，语义钉住。
+
+只用标准库 + 内存 SQLite，不联网。锁定点：
+- 统一身份：auto_memory._row_get 与 lifecycle._row_get 就是
+  peer_messages.row_get 本体（不是又一份复写）。
+- 真实行类型矩阵（None / dict / sqlite3.Row）下取值与回落
+  与三处旧版一致：现值原样回（含 0 / 空串等假值），缺列 /
+  缺键 / 空行回 default（默认 None）。
+- default 回落差异钉住：三处旧版的默认回落都是 None——
+  auto_memory 旧版 default 参数默认 None，lifecycle 旧版无
+  default 参数一律回 None，peer 旧版回 None；统一后两模块
+  调用处仍不传 default，缺失时仍为 None，不算改语义。
+- 统一路径实测：lifecycle.snapshot_to_dict 在 dict 缺键行与
+  sqlite3.Row 行上都经统一口出正确字段。
+"""
+
+import sqlite3
+import sys
+import unittest
+from pathlib import Path
+
+try:
+    import cloud.auto_memory as auto_memory
+    import cloud.lifecycle as lifecycle
+    from cloud.peer_messages import row_get
+except ImportError:
+    sys.path.insert(0, str(Path(__file__).resolve().parents[2]))
+    import cloud.auto_memory as auto_memory
+    import cloud.lifecycle as lifecycle
+    from cloud.peer_messages import row_get
+
+
+def _sqlite_row():
+    conn = sqlite3.connect(":memory:")
+    conn.row_factory = sqlite3.Row
+    try:
+        conn.execute("CREATE TABLE t(a TEXT, b INTEGER)")
+        conn.execute("INSERT INTO t(a, b) VALUES('x', 0)")
+        full = conn.execute("SELECT a, b FROM t").fetchone()
+        partial = conn.execute("SELECT a FROM t").fetchone()
+        return full, partial
+    finally:
+        conn.close()
+
+
+class RowGetUnifiedTestCase(unittest.TestCase):
+    def test_all_three_are_the_same_function(self):
+        self.assertIs(auto_memory._row_get, row_get)
+        self.assertIs(lifecycle._row_get, row_get)
+
+    def test_real_row_type_matrix(self):
+        full, partial = _sqlite_row()
+        # 现值原样回（含假值 0，不被当成缺失）。
+        self.assertEqual(row_get({"a": 0}, "a"), 0)
+        self.assertEqual(row_get({"a": ""}, "a"), "")
+        self.assertEqual(row_get(full, "a"), "x")
+        self.assertEqual(row_get(full, "b"), 0)
+        # 缺键 / 缺列 / 空行一律回 default（默认 None）。
+        self.assertIsNone(row_get({"a": 1}, "missing"))
+        self.assertIsNone(row_get(partial, "b"))
+        self.assertIsNone(row_get(None, "a"))
+        # 显式 default 只在缺失时生效，现值 None 也不被替换
+        #（旧 auto_memory 版同款语义：取到什么回什么）。
+        self.assertEqual(row_get({"a": 1}, "missing", default="d"), "d")
+        self.assertEqual(row_get(None, "a", default=7), 7)
+        self.assertIsNone(row_get({"a": None}, "a", default="d"))
+
+    def test_default_fallback_is_none_in_both_modules(self):
+        # 两模块调用处均不传 default；缺失回落必须仍是 None，
+        # 否则就是改了旧语义。
+        self.assertIsNone(auto_memory._row_get({}, "nope"))
+        self.assertIsNone(lifecycle._row_get({}, "nope"))
+        self.assertIsNone(auto_memory._row_get(None, "nope"))
+        self.assertIsNone(lifecycle._row_get(None, "nope"))
+
+    def test_lifecycle_snapshot_to_dict_via_unified_get(self):
+        out = lifecycle.snapshot_to_dict({"id": "s1", "task_id": "t1"})
+        self.assertEqual(out["id"], "s1")
+        self.assertEqual(out["task_id"], "t1")
+        self.assertIsNone(out["project_id"])
+        self.assertIsNone(out["branch"])
+        self.assertEqual(out["untracked"], [])
+        full, _partial = _sqlite_row()
+        out2 = lifecycle.snapshot_to_dict(
+            {"id": "s2", "untracked_json": '["a.txt"]'})
+        self.assertEqual(out2["untracked"], ["a.txt"])
+        # sqlite Row 行同样走统一口：缺列不炸。
+        self.assertIsNone(row_get(full, "untracked_json"))
+
+
+if __name__ == "__main__":
+    unittest.main()