[First PR] Add a simple contributor environment preflight command

[Ayush-Kumar0207]

Why this is a good first contribution

This task is intentionally scoped so you do not need to understand CodeVerse's editor, realtime system, database, AI, or deployment architecture. It is a small Node.js developer-experience utility with focused tests.

Problem

Contributors can discover an incompatible Node/npm version or an occupied local port only after setup has already started. A fast, offline preflight would make the first contribution less frustrating.

Your task

Create a root command named npm run doctor that:

• checks Node.js 22+;
• checks npm 10+;
• checks that the expected client/ and server/ directories exist;
• reports whether ports 3000 and 5000 are already occupied;
• prints plain-language fixes;
• makes no network requests and changes nothing on the contributor's machine.

Likely files

• new script under scripts/
• root package.json
• focused test file beside the script or in the existing script-test location
• CONTRIBUTING.md (one short command mention)

Definition of done

• npm run doctor works on a clean checkout;
• version parsing has focused tests;
• occupied-port output is understandable;
• blocking checks return non-zero, informational checks do not;
• no unrelated refactor.

Minimum verification

Run the focused test you add plus:

npm run doctor
npm run audit:repo

You do not need to run Docker, Redis, Supabase, hosted AI, or the full browser E2E suite for this issue.

If you want to work on this, comment I'd like to take this and the maintainer can help if setup gets in the way.