conventional-changelog/commitlint ? reverse-engineered prompt

Build me a small TypeScript tool that checks git commit messages and warns people when they don’t follow conventional commit format.

I want it to understand messages like feat: add login or fix(api): handle errors, and flag bad ones with a helpful explanation of what to change. It should work from the command line, and also be easy to run in a git hook or in CI so teams can stop bad commits before they land.

Please make it support a simple config file so I can customize the allowed types, the scope rules, and any message length limits. It would be great if it also had a clean reusable core so the checking logic can be used programmatically, not just through the CLI.

If you need to look up the current docs for conventional commits or modern Node setup, feel free to do that.