fix(action): skip checkout of missing image folder

[github-actions]

Closes #230

Applied changes based on Issue #230.

I’ve removed the failing git checkout on the untracked codex-comment-images folder and instead now clean it up by deleting that directory if it exists. Specifically:

• Added an import of Node’s fs.promises in src/github/action.ts.
• In the handleResult function, replaced:

  await execa('git', ['checkout', 'HEAD', '--', 'codex-comment-images'])

  with a call to fs.rm(..., { recursive: true, force: true }) wrapped in a try/catch.
• This ensures any dynamically downloaded images are removed without invoking Git on untracked paths.

Let me know if you’d like any further tweaks!