* Change loop variable name to avoid shadowing

The `i` index in the outermost loop over the nodes would become shadowed by the
`i` index in the inner loop over the cycle indices, so the check to exit early
would be done against the wrong variable.

* Exit processing a cycle as soon as it's broken

* Improve assertion error message

* fixup! Exit processing a cycle as soon as it's broken

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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