Upgrade eslint and add agents markdown to UI

[bbovenzi]

Body

We have a lot of people contributing code using AI tools. Problem is that we end up with a lot of code that doesn't follow our code standards.

1. Review and update our eslint rules to more explicitly enforce our best practices which may not be well recorded today. Especially, using semantic color tokens instead of specific colors (bg.subtle vs gray.50)

2. Add and maintain an agents.md file to give more context to AI prompts to follow practices that an eslint check cannot cover. Especially for translations, there can be many ways to translate a phrase, we should defer to any pre-existing terminology.

2. Update our contributing docs to have more specific instructions in markdown for both people and AI agents to read from

Please feel free to comment with other rules we should change.

Committer

• I acknowledge that I am a maintainer/committer of the Apache Airflow project.