Node.js compatibility: Bun.serve() in oauth.ts breaks browser OAuth on Node.js

[raylanlin]

Problem

src/auth/oauth.ts uses Bun.serve() in waitForCallback(), which is Bun-specific and not available in Node.js 18+.

// src/auth/oauth.ts ~line 90
const server = Bun.serve({ port, fetch(req) { ... } });

This causes minimax auth login (browser OAuth flow) to throw ReferenceError: Bun is not defined when run under Node.js.

Impact

• minimax auth login broken on Node.js
• minimax auth login --no-browser (device code flow) unaffected
• minimax auth login --api-key sk-xxxxx unaffected

Suggested Fix

Replace with Node.js built-in http.createServer().

Notes

Found while working on PR #29. Not including in that PR since auth module likely has dedicated ownership.