Remove AI code slop

Check the diff against the default branch and remove all AI-generated slop introduced in this branch.

Workflow

Step 1: Decide the base branch

Pick the most appropriate base ref in this order:

1. origin/main (if it exists)
2. origin/master (if it exists)
3. main (local)
4. master (local)

Use a base like <base> in the rest of the steps.

Step 2: Inspect the diff