Implement more robust and actual linting.

Much of the code is ai "augmented" and due to not really wanting to have a build process it's just vanilla JS. However eslint upgrading to 9.x and some of my favorite rulesets such as airbnb not being on 9.x I ether want to downgrade to 8 or look at something different.

No files, tests, or entry points are named. Start by reviewing the repository's current ESLint configuration and dependencies, then resolve whether ESLint 8 or an ESLint 9-compatible ruleset is the target. Done means the chosen linting setup runs successfully and provides the intended robust rules.

Written by the indexing model from the issue text.