Create a slash command file `.claude/commands/{{command}}.md`.

The file body is the prompt that runs when the user types `/{{command}} {{args}}`.

Structure:
1. One-line statement of the command's goal.
2. Steps to perform, each with a verification check.
3. What to output at the end (a summary, a diff, a report).

Use `$ARGUMENTS` where the user's args should be injected. Keep side effects explicit and ask before anything irreversible.