feat(sdk-android): throwaway sample app for SDK validation

Single-activity Android app that calls Uatu.start() in
SampleApplication.onCreate and registers three extractors
(app_state, click_count, uptime_millis). MainActivity has a
button so click_count exercises non-trivial state.

sdk/android/sample/build.gradle.kts

@@ -0,0 +1,36 @@
+plugins {
+    id("com.android.application") version "8.11.0"
+    kotlin("android") version "2.1.21"
+}
+
+android {
+    namespace = "dev.uatu.sample"
+    compileSdk = 35
+
+    defaultConfig {
+        applicationId = "dev.uatu.sample"
+        minSdk = 24
+        targetSdk = 35
+        versionCode = 1
+        versionName = "0.0.1"
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+
+    buildTypes {
+        debug {
+            isDebuggable = true
+        }
+    }
+}
+
+dependencies {
+    implementation(project(":sdk-android"))
+}

sdk/android/sample/src/main/AndroidManifest.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <application
+        android:name=".SampleApplication"
+        android:label="Uatu Sample"
+        android:allowBackup="false">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>

sdk/android/sample/src/main/kotlin/dev/uatu/sample/MainActivity.kt

@@ -0,0 +1,48 @@
+package dev.uatu.sample
+
+import android.app.Activity
+import android.graphics.Color
+import android.os.Bundle
+import android.view.Gravity
+import android.widget.Button
+import android.widget.LinearLayout
+import android.widget.TextView
+
+class MainActivity : Activity() {
+    companion object {
+        @Volatile var clickCount: Int = 0
+    }
+
+    private lateinit var label: TextView
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        val layout = LinearLayout(this).apply {
+            orientation = LinearLayout.VERTICAL
+            gravity = Gravity.CENTER
+            setBackgroundColor(Color.parseColor("#FAFAFA"))
+            setPadding(64, 96, 64, 64)
+        }
+
+        label = TextView(this).apply {
+            text = "Clicks: 0"
+            textSize = 28f
+            setTextColor(Color.BLACK)
+            gravity = Gravity.CENTER
+        }
+        layout.addView(label)
+
+        val button = Button(this).apply {
+            text = "Click me"
+            textSize = 18f
+            setOnClickListener {
+                clickCount++
+                label.text = "Clicks: $clickCount"
+            }
+        }
+        layout.addView(button)
+
+        setContentView(layout)
+    }
+}

sdk/android/sample/src/main/kotlin/dev/uatu/sample/SampleApplication.kt

@@ -0,0 +1,16 @@
+package dev.uatu.sample
+
+import android.app.Application
+import dev.uatu.sdk.Uatu
+
+class SampleApplication : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        Uatu.start(this)
+        Uatu.extract("app_state") { "running" }
+        Uatu.extract("click_count") { MainActivity.clickCount }
+        Uatu.extract("uptime_millis") { System.currentTimeMillis() - startedAt }
+    }
+
+    private val startedAt: Long = System.currentTimeMillis()
+}

settings.gradle.kts

@@ -19,3 +19,5 @@ rootProject.name = "uatu"
 include(":sidecar")
 include(":sdk-android")
 project(":sdk-android").projectDir = file("sdk/android")
+include(":sdk-android-sample")
+project(":sdk-android-sample").projectDir = file("sdk/android/sample")