chore: update flake.lock

[github-actions]

Automated changes by the update-flake-lock GitHub Action.

Flake lock file updates:

• Updated input 'nix-darwin':
    'github:lnl7/nix-darwin/d76299b' (2025-11-12)
  → 'github:lnl7/nix-darwin/d6c2f8a' (2026-01-28)
• Updated input 'nix-homebrew':
    'github:zhaofengli/nix-homebrew/a5409ab' (2026-01-26)
  → 'github:zhaofengli/nix-homebrew/842eeb8' (2026-07-15)
• Updated input 'nix-homebrew/brew-src':
    'github:Homebrew/brew/d01011c' (2026-01-25)
  → 'github:Homebrew/brew/6bd951d' (2026-07-14)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/c5296fd' (2026-01-23)
  → 'github:nixos/nixpkgs/241313f' (2026-07-19)

Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force