fix(gateway): keep in-browser WiFi boards reachable through the IoT gateway

The ESP32 examples now default to the in-browser JS engines, whose lwIP
serves the sketch's HTTP server from the simulation tab itself. Opening
the IoT gateway in a new tab backgrounds that tab, the browser throttles
its timers, and the in-chip server can't answer before the proxy's
timeout — the exact failure the Pico W iframe path already solved.

- WifiStatus grows an inBrowser flag (set by the overlay's JS bridges);
  the serial-monitor link and the WiFi badge now open the in-app iframe
  for any board that carries it, not just pi-pico-w.
- /api/gateway polls ~1s before answering 404: the net bridge dials on
  'got_ip', which races the sketch printing its URL, so a fast click
  used to land before the bridge registered.

backend/app/api/routes/iot_gateway.py

@@ -10,6 +10,7 @@ URL pattern:
     /api/gateway/{client_id}/{path}
     →  http://127.0.0.1:{hostfwd_port}/{path}
 """
+import asyncio
 import json
 import logging
 
@@ -66,17 +67,25 @@ async def gateway_proxy(client_id: str, path: str, request: Request) -> Response
             media_type='application/json',
         )
 
-    # ── ESP32: the server runs in QEMU, reachable via slirp hostfwd. ──
-    inst = esp_lib_manager.get_instance(client_id)
-    if inst and inst.wifi_enabled and inst.wifi_hostfwd_port != 0:
-        return await _proxy_esp32(inst, path, request)
+    # Registration races the sketch printing its URL: the in-browser engines
+    # dial their net bridge only on 'got_ip', which lands at the same moment
+    # "Server started at: ..." appears in the serial monitor — a fast click
+    # reaches here before the bridge exists. Poll briefly before giving up.
+    for attempt in range(5):
+        if attempt:
+            await asyncio.sleep(0.25)
 
-    # ── Pico W (and any other overlay-provided board): the server runs in the
-    #    browser-side lwIP, reachable only by the overlay proxying TCP into the
-    #    chip over the WS bridge. OSS has no resolver -> falls through to 404. ──
-    overlay_resp = await dispatch_gateway_proxy(client_id, path, request)
-    if overlay_resp is not None:
-        return overlay_resp
+        # ── ESP32: the server runs in QEMU, reachable via slirp hostfwd. ──
+        inst = esp_lib_manager.get_instance(client_id)
+        if inst and inst.wifi_enabled and inst.wifi_hostfwd_port != 0:
+            return await _proxy_esp32(inst, path, request)
+
+        # ── Pico W (and any other overlay-provided board): the server runs in
+        #    the browser-side lwIP, reachable only by the overlay proxying TCP
+        #    into the chip over the WS bridge. OSS has no resolver -> None. ──
+        overlay_resp = await dispatch_gateway_proxy(client_id, path, request)
+        if overlay_resp is not None:
+            return overlay_resp
 
     return Response(
         content='{"error":"No WiFi-enabled board found for this client. Make sure your sketch connected to WiFi and started a server on port 80."}',

frontend/src/components/simulator/SerialMonitor.tsx

@@ -311,7 +311,15 @@ export const SerialMonitor: React.FC = () => {
                   const gatewayUrl = `${backendBase}/gateway/${clientId}${path}`;
 
                   parts.push(text.slice(lastIdx, start));
-                  const isPicoW = activeBoard.boardKind === 'pi-pico-w';
+                  // Boards whose network stack lives in THIS tab (Pico W, and
+                  // any ESP32 on the in-browser JS engine — wifiStatus carries
+                  // inBrowser) must open in the in-app iframe: a new tab
+                  // backgrounds this one, the emulation gets timer-throttled,
+                  // and the in-chip server times out. QEMU boards run
+                  // backend-side, so a new tab is fine there.
+                  const servesInTab =
+                    activeBoard.boardKind === 'pi-pico-w' ||
+                    activeBoard.wifiStatus?.inBrowser === true;
                   parts.push(
                     <a
                       key={i}
@@ -319,10 +327,8 @@ export const SerialMonitor: React.FC = () => {
                       target="_blank"
                       rel="noreferrer"
                       onClick={
-                        isPicoW
+                        servesInTab
                           ? (e) => {
-                              // Pico W runs in this tab; a new tab freezes the
-                              // emulation. Show the page in an in-app iframe.
                               e.preventDefault();
                               openDeviceGateway(gatewayUrl);
                             }

frontend/src/components/simulator/SimulatorCanvas.tsx

@@ -2806,9 +2806,16 @@ export const SimulatorCanvas = ({ headerSlot }: SimulatorCanvasProps = {}) => {
                         }
                       ).__velxio_iot_gateway_open_gate__;
                       if (gate && gate()) return;
-                      // Pico W runs in THIS tab — a new tab would background and
-                      // freeze the emulation. Show the page in an in-app iframe.
-                      if (activeBoard.boardKind === 'pi-pico-w') {
+                      // Boards whose network stack lives in THIS tab (Pico W,
+                      // and any ESP32 on the in-browser JS engine — wifiStatus
+                      // carries inBrowser) open in the in-app iframe: a new tab
+                      // backgrounds this one, the emulation gets timer-throttled,
+                      // and the in-chip server times out. QEMU boards run
+                      // backend-side, so a new tab is fine there.
+                      if (
+                        activeBoard.boardKind === 'pi-pico-w' ||
+                        activeBoard.wifiStatus?.inBrowser === true
+                      ) {
                         openDeviceGateway(gatewayUrl);
                       } else {
                         window.open(gatewayUrl, '_blank');

frontend/src/simulation/Esp32Bridge.ts

@@ -108,6 +108,11 @@ export interface WifiStatus {
   status: string;
   ssid?: string;
   ip?: string;
+  /** True when the board's network stack lives in THIS browser tab (in-browser
+   *  JS engine). The IoT gateway must then open in the in-app iframe: a new
+   *  tab backgrounds this one, the emulation gets timer-throttled, and the
+   *  in-chip HTTP server can't answer. Unset = server runs backend-side. */
+  inBrowser?: boolean;
 }
 export interface BleStatus {
   status: string;

frontend/src/types/board.ts

@@ -100,6 +100,11 @@ export interface WifiStatus {
   status: string; // 'initializing' | 'connected' | 'got_ip' | 'disconnected'
   ssid?: string;
   ip?: string;
+  /** True when the board's network stack lives in THIS browser tab (in-browser
+   *  JS engine). The IoT gateway must then open in the in-app iframe: a new
+   *  tab backgrounds this one, the emulation gets timer-throttled, and the
+   *  in-chip HTTP server can't answer. Unset = server runs backend-side. */
+  inBrowser?: boolean;
 }
 
 export interface BleStatus {