Pass currentSystem to NixOS-integrated home-manager extraSpecialArgs (flakes-sytx)

nixos-rebuild on g1 fails with infinite recursion in packs/home/host because the NixOS-integrated home-manager module (packs/nixos/common/settings/home-manager.nix) doesn’t pass currentSystem via extraSpecialArgs. Standalone home configurations get it via flake/home-configs.nix but NixOS hosts that use home-manager.users.* don’t.

Summary of Changes

Updated packs/nixos/common/settings/home-manager.nix to:

• Take pkgs as module argument
• Pass currentSystem = pkgs.stdenv.hostPlatform.system via extraSpecialArgs

This mirrors what flake/home-configs.nix already does for standalone home configurations. The integrated home-manager NixOS module evaluates packs/home/host (via home/yjpark.nix imported through packs/nixos/host/yjpark.nix), and that module reads currentSystem in its imports to conditionally include the linux subdirectory.

Verified: g1 evaluation now progresses past the recursion point (fails only on an unrelated network fetch of Smithay/smithay.git).