normify: regenerate the archive branch on the next map rebuild #10

The Normify artifact now lives on the orphan normify branch instead of the code tree (PR #6); the README indexes it there.

Convention: the branch is updated only when the map is rebuilt (it is frozen at source commit 6d203c0). When Normify runs next, push the new normify-pyvdisk/ to that branch and update the frozen-commit note in both the branch README and the main README. Consider a make normify-sync or CI job so the sync is one command and the fingerprints in receipt.json stay the source of truth.