Bun import of .html files returns HTMLBundle (not a string) in Vercel's
serverless environment, and Bun.file() has no filesystem access there.
Copy the HTML content into api/test-api-content.ts as an escaped string
export, then import it in api/relay.ts — Bun bundler inlines it.
Co-Authored-By: Claude <noreply@anthropic.com>
