feat(sim): web viewer at /sim + touch injection at /api/sim/touch

- GET /sim: live viewer page, 2s screenshot refresh, click-to-touch
- POST /api/sim/touch?x,y,down: injects into sdl-pointer backend,
  auto-releases after 1.5s; simulator-only (404 on ESP32)
- sdl_input: file-scope touch override state with extern C setters

Devices/simulator/Source/drivers/sdl_input.cpp

@@ -14,6 +14,34 @@ constexpr size_t KEY_QUEUE_CAPACITY = 32;
 
 SdlPointerState pointer_state = { 0, 0, false };
 
+} // namespace
+
+// Web touch-injection override (headless sim viewer). Guarded by tick count so
+// a press auto-releases even if the viewer never sends the release event.
+// File-scope (not anonymous namespace): the extern "C" setters below must be
+// visible to the linker for WebServerService's touch endpoint.
+bool touch_override_active = false;
+SdlPointerState touch_override = { 0, 0, false };
+uint32_t touch_override_until_tick = 0;
+#define SIM_TOUCH_HOLD_MS 1500
+
+extern "C" void sdl_input_set_touch_override(int32_t x, int32_t y, bool pressed) {
+    touch_override.x = x;
+    touch_override.y = y;
+    touch_override.pressed = pressed;
+    touch_override_active = pressed;
+    if (pressed) {
+        touch_override_until_tick = SDL_GetTicks() + SIM_TOUCH_HOLD_MS;
+    }
+}
+
+extern "C" void sdl_input_clear_touch_override(void) {
+    touch_override_active = false;
+    touch_override.pressed = false;
+}
+
+namespace {
+
 uint32_t key_queue[KEY_QUEUE_CAPACITY];
 size_t key_queue_head = 0;
 size_t key_queue_count = 0;
@@ -70,7 +98,7 @@ uint32_t keycode_to_key(SDL_Keycode sdl_key, bool shift) {
     }
 }
 
-}
+} // namespace
 
 void sdl_input_pump() {
     if (!text_input_started) {
@@ -125,6 +153,17 @@ void sdl_input_pump() {
 }
 
 void sdl_input_get_pointer_state(SdlPointerState* out_state) {
+    if (touch_override_active) {
+        // Auto-release: viewer sends press only; LVGL needs press then release
+        // to register a click. Hold long enough for several indev polls.
+        if ((int32_t)(SDL_GetTicks() - touch_override_until_tick) >= 0) {
+            touch_override_active = false;
+            touch_override.pressed = false;
+        } else {
+            *out_state = touch_override;
+            return;
+        }
+    }
     *out_state = pointer_state;
 }