fix: stabilize workspace gateway and scaffolding

packages/dev-server/README.md

@@ -147,7 +147,7 @@ Serves several apps behind one port and routes each request to the right app by
 ```ts
 interface GatewayOptions {
   port?: number; // default 3000
-  hostname?: string; // default "localhost"
+  hostname?: string; // dev: "127.0.0.1"; production: "0.0.0.0"
   mode?: "development" | "production";
   apps: GatewayApp[];
   security?: GatewaySecurity;
@@ -176,7 +176,10 @@ interface GatewaySecurity {
 }
 ```
 
-The gateway exposes `/__gateway/health` (JSON list of routed apps) and returns a `RunningGateway` (`{ port, url, stop() }`).
+Open the gateway URL (normally `http://127.0.0.1:3000`), not an app's internal
+port. The gateway exposes `/__gateway/health` (JSON list of routed apps) and returns a
+`RunningGateway` (`{ port, url, stop() }`). Use `--host=0.0.0.0` when other devices need
+to reach a development gateway.
 
 ### `node:http` adapter (from `./adapters/node.ts`)