Migrate tests to Vitest 4

[kentcdodds]

Summary

• migrate the repo from bun:test to vitest
• add dedicated Vitest configs for general and unit-only runs
• update Wrangler-backed integration tests to run under Node-backed Vitest using Node subprocess APIs
• refresh CI and testing docs to use the new Vitest commands

Testing

• bun run test:unit
• bunx vitest run mock-servers/resend/resend-mock.test.ts
• bun run test:mcp
• bun run typecheck && bun run lint

  

[github-actions]

🔎 Preview deployed: https://epicflare-pr-67.kentcdodds.workers.dev

Worker: epicflare-pr-67
D1: epicflare-pr-67-db
KV: epicflare-pr-67-oauth-kv

Mocks:

• ai: https://epicflare-pr-67-mock-ai.kentcdodds.workers.dev/__mocks (epicflare-pr-67-mock-ai)
• resend: https://epicflare-pr-67-mock-resend.kentcdodds.workers.dev/__mocks (epicflare-pr-67-mock-resend)

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

^{Reviewed by Cursor Bugbot for commit 64273a7. Configure here.}