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/auto_memory.py

@@ -53,12 +53,15 @@ cloud/migrations.py 的对齐说明；PG DDL 同步进
 cloud/db.py POSTGRES_SCHEMA 与 MIGRATION_TABLES。
 """
 
-import os
 import re
 import time
 
 from cloud.db import connect as _db_connect
 from cloud.identity import IdentityStore
+# 行取值统一走 peer_messages.row_get（A7）：本模块旧私有版与之
+# 同款语义（缺列/缺键/空行回 default，默认 None），调用处仍
+# 用 _row_get 别名，行为不变。
+from cloud.peer_messages import row_get as _row_get
 from cloud.quota import default_quota_usd_micros as _quota_default
 from cloud.quota import monthly_usage as _quota_monthly_usage
 from cloud.quota import quota_for_owner as _quota_for_owner
@@ -152,13 +155,6 @@ def quota_remaining_percent(db_path, owner):
         conn.close()
 
 
-def _row_get(row, name, default=None):
-    try:
-        return row[name]
-    except (KeyError, IndexError, TypeError):
-        return default
-
-
 def _first_line(text, max_len=200):
     for line in (text or "").splitlines():
         line = " ".join(line.split())