Xubin Ren c1957e14ff refactor(memory): centralize cursor validation behind a single gate
Move the non-int cursor guard out of the two consumer sites and into a
shared ``_iter_valid_entries`` iterator so the invariant lives in one
place.  Closes three gaps left by the original fix:

* ``bool`` is now rejected — ``isinstance(True, int)`` is ``True`` in
  Python, so the previous guard silently treated ``{"cursor": true}`` as
  cursor ``1``.
* Recovery now returns ``max(valid cursors) + 1``.  Under adversarial
  corruption "first int scanning in reverse" is not the same thing, and
  only ``max`` keeps the recovered cursor strictly greater than every
  legitimate cursor still on disk.
* Non-int cursors are logged exactly once per ``MemoryStore``.  Silently
  dropping corrupted entries hides the root cause (an external writer
  to ``memory/history.jsonl``); rate-limiting keeps the log clean when
  the same poisoned file is read every turn.

All 7 tests from the original fix pass unchanged; 3 new tests pin the
invariants above.

Made-with: Cursor
2026-04-21 14:02:53 +08:00
..