feat(sim): board feature parity (reset/GPS/sensors/admin/keyboard) + input fixes

Rounds out the browser sim harness with the rest of the physical board's
interactions: a reset button (JS-driven, since board.reboot() is inert
under -sEXIT_RUNTIME=0), GPS input wired into a real LocationProvider via
new SimSensorManager, JS-settable battery/environment telemetry, an
admin/repeater-login test hook (sendRoomLogin against the default
"password"), and full physical-keyboard text entry (printable ASCII
passthrough into the existing KeyboardWidget, Tab->KEY_KB_ENTER submit).

Also fixes three real bugs found while exercising all of this in a real
browser:
- UITask.cpp's native-only stdin poll branch had no __EMSCRIPTEN__
  exclusion, so it also compiled into the wasm build and called a real,
  blocking window.prompt() on nearly every frame -- the actual cause of
  the reported time/controls jumping. Now gated to native only.
- 'n'/'p' were mapped as Next/Prev keyboard shortcuts, colliding with
  typing those literal letters. Removed the shortcuts; added explicit
  Next/Prev buttons to mesh.html (previously relied solely on them).
- Buttons grabbed native browser keyboard focus on click, so a later
  stray Enter/Space could silently re-trigger a previously-clicked button
  (e.g. Reset). mousedown now calls preventDefault() on all buttons.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

variants/sim/target.cpp

@@ -9,12 +9,32 @@ SimSerialClass Serial;
 SimMainBoard board;
 SimRadio radio_driver;
 SimRTCClock rtc_clock;
-SensorManager sensors;   // base class: no real sensors in Phase 1
+// Phase 4: SimSensorManager wires in the sim's GPS + one JS-settable
+// environment channel -- see SimSensorManager.h (its methods' bodies are
+// defined further down in this file, not there, for the reason explained
+// in that header's comment).
+SimSensorManager sensors;
 
 #ifdef DISPLAY_CLASS
 DISPLAY_CLASS display;
 #endif
 
+// SimSensorManager's methods (see that header's comment on why they're
+// defined here rather than inline).
+LocationProvider* SimSensorManager::getLocationProvider() {
+  return &sim_location_provider();
+}
+
+bool SimSensorManager::querySensors(uint8_t requester_permissions, CayenneLPP& telemetry) {
+  if ((requester_permissions & TELEM_PERM_LOCATION) && sim_location_provider().isValid()) {
+    telemetry.addGPS(TELEM_CHANNEL_SELF, (float)node_lat, (float)node_lon, (float)node_altitude);
+  }
+  if (requester_permissions & TELEM_PERM_ENVIRONMENT) {
+    telemetry.addTemperature(TELEM_CHANNEL_SELF + 1, envTemperatureRef());
+  }
+  return true;
+}
+
 bool radio_init() {
   // No real radio hardware to initialise -- always succeeds (see
   // variants/sim/SimRadio.h; Phase 3 of the sim plan is where two SimRadio
@@ -28,7 +48,15 @@ mesh::LocalIdentity radio_new_identity() {
   return mesh::LocalIdentity(&rng);
 }
 
-#ifdef __EMSCRIPTEN__
+// DISPLAY_CLASS too, not just __EMSCRIPTEN__: SimDisplayDriverCanvas itself
+// only exists when DISPLAY_CLASS is defined (target.h only #includes
+// SimDisplayDriver.h -- where the class lives -- inside its own #ifdef
+// DISPLAY_CLASS block), and the headless repeater/room_server wasm builds
+// never define DISPLAY_CLASS at all. This was a latent gap from the
+// pixel-perfect-font change (companion_radio's own build_wasm.sh happens to
+// always define DISPLAY_CLASS, so it never surfaced there) -- only found now
+// that build_wasm_repeater.sh got rebuilt for Phase 4.
+#if defined(__EMSCRIPTEN__) && defined(DISPLAY_CLASS)
 // Real bitmap-font text rendering for SimDisplayDriverCanvas::print()
 // (declared in SimDisplayDriver.h, defined here -- the one TU allowed to
 // include MiscFixedRenderer.h; see that header's own "include only from a