Improve documentation and add contributing guide

[delphiactual]

README.md improvements:

• Add project description and link to DIM
• Add prerequisites section (Node.js >=22, pnpm >=10, API key)
• Improve command documentation with better examples
• Rewrite "Output Files" section with clearer descriptions
• Remove outdated husky v8 troubleshooting
• Add documentation links section

CONTRIBUTING.md (new):

• Comprehensive contributing guide for new contributors
• Setup instructions and development workflow
• Code style guidelines and project structure overview
• Generator script creation guide with module caching pattern
• Testing, commit, and PR guidelines
• Common tasks and troubleshooting
• Golden rule: never manually edit JSON files

[chainrez]

In true LLM fashion, I am assuming from sheer amount of text and cheerful emojis, this is exhaustingly much to read.

I feel like some of it covers the very concept of reading and understanding code, the concept of troubleshooting etc, like explaining to console log things seems outside of the purview of "how to change something in specifically d2ai."

But on the whole a net positive in terms of explanation.