* fix(memory): restore facts from older backups
Use the current snapshot revision for existing facts during backup import so saved contents can be restored after later edits. Preserve manifest and fact preconditions, scope isolation, and caller-owned input data.
* refactor(memory): share import revision preconditions
* docs(memory): fit import guidance within chain budget
* fix(memory): validate backup revisions before restoration
---------
Co-authored-by: liyinlong <173714821+lilong555@users.noreply.github.com>
