Scrubbed remaining upstream references and solidified Nomarchy's identity:
- Replaced 'Omarchy' and 'Spirit of Omarchy' with brand-independent terms in README.md and scripts.
- Updated nomarchy-welcome banner to 'The Professional NixOS Desktop'.
- Set nomarchy-version codename to 'Sovereign'.
- Verified core/system/branding.nix for OS-release and bootloader labels.
- Verified SDDM and Plymouth metadata for correct branding.
- Updated ROADMAP.md board.