Summary

• Adds focused Vitest coverage for Studio Basic Auth rejection and valid response paths.
• Checks the generated Studio HTML query bridge posts to /query/raw with the configured API key.
• Covers StudioPlugin metadata and custom-prefix route registration.

Refs #71 /claim #71

Tests

• pnpm exec vitest run plugins/studio/handler.test.ts
• pnpm exec prettier --check plugins/studio/handler.test.ts
• git diff --check