Add src/middleware/error.ts with a four-argument Express error handler
that logs errors server-side via console.error and responds with HTTP
500 and a generic { error: 'Internal server error' } body, never
leaking stack traces to the client. Register it last in a new
src/server.ts entry point.
Add src/placeholder.test.ts to confirm the Vitest harness works
end-to-end (npm test passes). Update CLAUDE.md project structure
to reflect the now-created src/ directory.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
