feat: restore gateway HMR and add WRN formatting

packages/dev-server/test/gateway.test.ts

@@ -4,6 +4,7 @@ import {
   forwardAuthFailure,
   forwardAuthHeaders,
   gatewayProxyHeaders,
+  gatewayRestartDelay,
 } from "../src/gateway.ts";
 
 test("gateway uses platform-safe hostname defaults", () => {
@@ -56,3 +57,11 @@ test("forward auth describes the original gateway request", () => {
   expect(headers.get("cookie")).toBe("session=abc");
   expect(headers.get("authorization")).toBe("Bearer token");
 });
+
+test("gateway respawns development apps after an HMR restart exit", () => {
+  expect(gatewayRestartDelay("development", 97, null)).toBe(0);
+  expect(gatewayRestartDelay("development", 1, null)).toBe(1200);
+  expect(gatewayRestartDelay("development", 0, null)).toBeNull();
+  expect(gatewayRestartDelay("development", 97, "SIGTERM")).toBeNull();
+  expect(gatewayRestartDelay("production", 97, null)).toBeNull();
+});