CI: build debug APK on push to main and upload as artifact

.github/workflows/build-apk.yml

@@ -0,0 +1,49 @@
+name: Build APK
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+concurrency:
+  group: build-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Build debug APK
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - name: Set up Android SDK
+        uses: android-actions/setup-android@v3
+
+      - name: Build debug APK
+        run: |
+          ./gradlew :app:assembleThirdPartyDebug --no-daemon --stacktrace
+
+      - name: Upload APK artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: openclaw-android-heartbeat-debug
+          path: app/build/outputs/apk/thirdParty/debug/*.apk
+          if-no-files-found: error
+          retention-days: 30
+
+      # Future: release builds — add keystore secrets (ANDROID_KEYSTORE_BASE64,
+      # ANDROID_KEYSTORE_PASSWORD, ANDROID_KEY_ALIAS, ANDROID_KEY_PASSWORD) to
+      # repo secrets, then add a `release` job that signs and uploads to
+      # GitHub Releases.