feat(net): start wifi after Lua and keep the radio transient

The driver is started once the runtime has allocated, so its first init faces
the same heap as every later one; against a pristine boot heap it wins blocks
that cannot be reassembled. Only the boot sync powers the radio down, so an
explicit connect stays up. Polling a powered-off driver silently re-inits it,
which is what spammed esp_wifi_init failures, so status and loop now check the
mode first. A failed new otherwise reboots with a bare backtrace; the handler
logs the heap instead.

src/main.cpp

@@ -7,6 +7,9 @@
 #include <TFT_eSPI.h>
 #include <XPT2046_Touchscreen.h>
 
+#include <new>
+
+#include "heaplog.h"
 #include "host/lua_host.h"
 #include "net.h"
 #include "settings.h"
@@ -42,6 +45,16 @@ static void fallbackScreen(const char *message) {
 
 void setup() {
   Serial.begin(115200);
+
+  // A failed new otherwise unwinds to terminate() and a bare abort backtrace.
+  // Nothing can be freed at that point, so this only buys a legible cause.
+  std::set_new_handler([]() {
+    logHeap("oom");
+    Serial.println("[fatal] out of memory");
+    Serial.flush();
+    ESP.restart();
+  });
+
   tft.begin();
   tft.setRotation(0);
   tft.fillScreen(TFT_WHITE);
@@ -58,6 +71,7 @@ void setup() {
   net::begin();
   if (!host.begin())
     fallbackScreen("home failed to start");
+  net::startWifi();
 }
 
 void loop() {