Archive a submission: checksum duplicates, trash not delete

When a user asks to 'clear Downloads' and archive a finished submission into a repo, first map every related file and compare checksums (shasum) against copies already in the repo, so only exact duplicates are discarded. Move discarded duplicates to ~/.Trash (with a unique name if one exists) instead of rm, so nothing is permanently deleted. Leave unrelated personal files untouched and say so. Put the exact submitted files in one archive folder with a tiny README mapping each file to the form question it answered, separate drafts from superseded versions, and update any docs whose links pointed at the old folder names (grep for the old path afterwards).