- Add repos { } block to system config with named repos, channels,
mirrors, and priority
- Add index "name" { } file format for package indexes
- Add kappa index <dir> subcommand that scans .kap files and
generates index.kap
- parse_index() and build_index() in DSL module
- format_index() roundtrip support in tools module
- validate and format subcommands handle all three formats
(package, config, index) with automatic detection
- Backward compatible: remotes = [...] still works unchanged
