docs: rewrite README for v1 release

[lcottercertinia]

Summary

• Restructure README with Quick Start, What You Can Do, and Tools Reference sections
• Add hero image, badges (npm, CI), and cleaner navigation
• Improve execute_anonymous docs with debug level categories and usage notes
• Remove duplicate content (Features list vs Tools section, redundant config block)
• Clean up formatting (emoji headings, anchor links, stray raw URL)

Test plan

• Verify README renders correctly on GitHub
• Check all anchor links resolve
• Confirm image loads from main branch