- Change from showing version to build format: 'hash dd/mm/yy H:M:S'
- Parse nixos-version output to extract short hash and format date
- Update system widget to display 'Build:' instead of 'Version:'
- Remove version/build_date fields in favor of single build string
- Follow TODO.md specification for NixOS section layout
- Create NixOS collector for version and active users detection
- Add SystemWidget combining all system information in TODO.md layout
- Replace separate CPU/Memory widgets with unified system display
- Add tree structure for storage with drive temperature/wear info
- Support NixOS version, active users, load averages, memory usage
- Follow exact decimal formatting from specification
