Network fault injection in tests (useToxiproxy)

Wraps a real dependency (e.g. Redis, an upstream HTTP service) behind a Toxiproxy proxy so tests can inject latency, bandwidth limits, or full outages and assert the app degrades/retries correctly. Demonstrated in toxiproxy-demo.test.ts.

Calling useToxiproxy() with no config just starts the Toxiproxy container itself, without declaring a proxy — call it without config and without declaring proxies only if you plan to add proxies later; otherwise declare proxies up front:

const {useToxiproxy} = useNodeBoot(EmptyApp, ({useToxiproxy}) => {
    useToxiproxy({
        proxies: [{name: "redis", upstream: "localhost:6379"}],
    });
});