flake.lock: Update

Flake lock file updates:

• Updated input 'ghostty':
    'github:ghostty-org/ghostty/e5b65a2' (2026-06-27)
  → 'github:ghostty-org/ghostty/28f9367' (2026-06-29)
• Updated input 'helix':
    'github:helix-editor/helix/6b7c7c6' (2026-06-24)
  → 'github:helix-editor/helix/278b243' (2026-06-29)
• Updated input 'home-manager':
    'github:nix-community/home-manager/8d8a6cc' (2026-06-27)
  → 'github:nix-community/home-manager/5d72a29' (2026-06-29)
• Updated input 'lib-aggregate':
    'github:nix-community/lib-aggregate/89fd755' (2026-06-21)
  → 'github:nix-community/lib-aggregate/93fd151' (2026-06-28)
• Updated input 'lib-aggregate/nixpkgs-lib':
    'github:nix-community/nixpkgs.lib/2b737a4' (2026-06-21)
  → 'github:nix-community/nixpkgs.lib/db3f255' (2026-06-28)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/89570f2' (2026-06-23)
  → 'github:nixos/nixpkgs/534ee3d' (2026-06-28)

Author: colemickens