Four call sites repeated lock, snapshot, try/except, restore. Each used
restore_table_versions, which restores in _tables() order — documents
first, contradicting RESTORE_TABLE_ORDER — and each caught Exception, so
a cancellation mid-write skipped rollback and left the earlier table
writes committed.
Store.write_transaction() holds the lock, snapshots under it, and rolls
back through _rollback_to_snapshot: RESTORE_TABLE_ORDER, shielded from
cancellation, absorbed cancellation re-delivered, rollback failure raised
with the original as cause. The two single-table update_meta sites keep
the bare lock.
The batch documents write moves inside the guarded body; it was outside
the try, so a failure there was never rolled back. Auto-vacuum is
scheduled after the transaction rather than inside it.
restore_table_versions is removed; those four sites were its only callers.
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