Refactor shared `FilterArgs` and `build_group_filter` to return a `Result` with explicit validation for fraction bounds, min/max ordering, and count constraints. Update conditional defaults for `--min-frac` and `--max-outgroup-count` to depend on explicit quorum flags, preventing silent configuration conflicts. Update documentation and MkDocs navigation to reflect the new centralized k-mer filtering system across `rebuild`, `dump`, and `unitig` commands.
Eric Coissac