Upgrade Path Testing

A fresh install and an upgrade are different products. Prove both.

Contract

Test at least:

1. empty profile → current version;
2. previous version (supported) → current version;
3. partially configured previous install → current version;
4. rerun current installer over current version.

For upgrades, preserve user-owned configuration, credentials, caches worth retaining, project data, and unrelated files. Replace only bundle-owned state. Validate migrations before deleting old data and keep rollback/backup material until the new state passes its doctor.

Compare the post-upgrade effective configuration with a fresh install plus the user's intentional customizations. A successful fresh install does not prove the upgrade path.