Covers: option-already-declared (duplicate mkOption), attribute-missing
(forgot to import nomarchy.nixosModules.system), Stylix target conflict
(needs lib.mkForce, not bare bool), home-manager .hm-bak churn (left over
from backupFileExtension after first install), and impermanence path
missing (dir not in environment.persistence list).
Each entry has the literal error text, the cause, and a copy-paste fix.
Linked from README.md and docs/MIGRATION.md so users hit it before
guessing.
Keeps every long-form doc under docs/ — only README.md remains at the
repo root. Updates the two references (README.md, docs/ROADMAP.md).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
