Enable Developer Certificate of Origin (DCO) for Chisel Repositories

**Description**

As part of the LF project onboarding cleanup, our Project Formation Team has recommended implementing a [Developer Certificate of Origin](http://developercertificate.org) (DCO) across the Chisel repositories (and other CHIPS projects).

The DCO ensures that all code contributions are signed off, verifying that contributors agree to the terms of open-source development. This helps maintain compliance and transparency in our repositories.

**Task**

Enable the DCO GitHub App on Chisel repositories using [Probot DCO](https://probot.github.io/apps/dco/).

@jackkoenig for visibility and possibly implementation.

Start with the issue's Probot DCO link and the GitHub App configuration for the Chisel repositories. Confirm which repositories are in scope and what permissions or onboarding steps are required; done means DCO enforcement is enabled across the agreed repositories and contributions are checked for sign-off.

Written by the indexing model from the issue text.