feat(hyprctl): add split CLI and expose it via Nix

[rrvsh]

Summary

• add a new Rust CLI crate (hyprctl-split) that reads workspace/window state from hyprctl, applies a 1:2 left/right split for two-window workspaces, and verifies the result
• expose hyprctl-split as a flake package in nix/outputs/packages.nix
• include the package in home.packages for the rafiq Home Manager profile in nix/modules/aliases.nix

Validation

• cargo test --manifest-path rs/Cargo.toml --all
• cargo clippy --manifest-path rs/Cargo.toml --all
• just check
• manual run of hyprctl-split (dry-run and apply) on workspace 3