Document Cursor native plugin testing

[chubes4]

Summary

• document Cursor native plugin install and validation flow
• add generated output guidance for native Cursor testing
• extend verification coverage for Cursor-specific testing notes

Testing

• pnpm build
• pnpm verify
• pnpm export:cursor -- --dry-run

Refs #79

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Drafted the Cursor native plugin documentation and verification updates; Chris remains responsible for review and testing.