af7f0078bc
A filesystem-imported archive with no adjacent sidecar has no Post, so _post_for_sidecar returns None — and the milestone-#87 stamp call dereferenced post.id. _stamp_member_archive already no-ops on a None post_id (no post → no provenance to stamp); pass None instead of crashing. Caught by the existing test_reimport_archive_is_idempotent (no-sidecar zip). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>