- Remove deleted fonts.nix from directory layout
- Update 'Adding a New Program' section to reflect ponytail cleanup: simple packages go in common.nix, per-file only for programs needing real configuration
- Update Rules section to document common.nix and per-file program patterns
Resolves conflict with upstream tmux/blender additions (already covered
by the per-program restructure). Adds weekly nix GC (--delete-older-than 7d),
store auto-optimise, and project CLAUDE.md.
