Running `pnpm dev` alone gave ECONNREFUSED on every request, because nothing
was listening on :7788. Two separate causes:
- the backend simply was not running, and
- Vite bound [::1]:5173 while the proxy target was "localhost", which Node
resolves to ::1 first. The Go server binds IPv4, so even with the backend up
the proxy could fail before falling back.
- vite.config.ts: proxy target is now 127.0.0.1 explicitly and overridable via
VELLUM_API; server.host is true so both stacks are served.
- scripts/dev.sh + `make dev`: builds the backend, waits for /healthz, starts
Vite, and stops the backend on exit. Ctrl-C tears down both.
- README documents that running Vite alone needs the backend already up.
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