chore: Fix demo build.gradle.kts and improve Red App getting started docs

examples/demo/GettingStarted.md

@@ -69,7 +69,17 @@ Alternatively, from the terminal:
 ./gradlew :app:installGmsDebug
 ```
 
-The app ships with a default OneSignal App ID (`77e32082-ea27-42e3-a898-c72e141824ef`). To use your own, change it in the **App** section at the top of the running app.
+The app ships with a default OneSignal App ID (`77e32082-ea27-42e3-a898-c72e141824ef`).
+
+**Changing the App ID requires uninstalling and reinstalling the app for it to take effect.**
+
+To use your own App ID, update the `onesignal_app_id` value in `app/src/main/res/values/strings.xml`:
+
+```xml
+<string name="onesignal_app_id">YOUR_APP_ID_HERE</string>
+```
+
+Then uninstall the app from the device/emulator and run it again.
 
 Once launched, you should see the following screen:
 

examples/demo/app/build.gradle.kts

@@ -4,7 +4,8 @@ plugins {
     id("org.jetbrains.kotlin.plugin.compose") version "2.2.0"
 }
 
-val kotlinVersion: String by rootProject.extra
+// Keep IDE sync stable even if root extra properties are unavailable.
+val kotlinVersion: String = rootProject.findProperty("kotlinVersion") as? String ?: "2.2.0"
 
 // Apply GMS or Huawei plugin based on build variant
 // Check at configuration time, not when task graph is ready

examples/demo/build.gradle.kts

@@ -1,9 +1,7 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
-val kotlinVersion by extra("2.2.0")
-
 buildscript {
-    val kotlinVersion: String by extra
+    val kotlinVersion by extra("2.2.0")
     repositories {
         google()
         mavenCentral()