Android CI: fail the build on a Gradle error + surface the real cause

The build step ended with `find … *.apk`, which exits 0 even when Gradle failed
and no APK exists — so Codemagic marked a failed Gradle run as a green build with
no artifact. Now: capture gradle output, use PIPESTATUS to detect failure, print
the "What went wrong" / FAILURE block, exit non-zero, and assert an APK exists.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

codemagic.yaml

@@ -231,12 +231,26 @@ workflows:
 
       - name: Build the debug APK
         script: |
+          set -e
           cd mobile/android
           chmod +x ./gradlew
           # Debug build type is auto-signed with the Android debug keystore → directly installable, no Play
           # account or upload key needed. (A signed release AAB for the Play Store is a later, separate step.)
-          ./gradlew assembleDebug --stacktrace
+          # Capture the output so that, on failure, we surface Gradle's actual "What went wrong" block instead
+          # of a wall of internal stack frames — and FAIL the step (a trailing `find` used to exit 0 and mask it).
+          set +e
+          ./gradlew assembleDebug --stacktrace 2>&1 | tee /tmp/gradle.log
+          STATUS=${PIPESTATUS[0]}
+          set -e
+          if [ "$STATUS" != "0" ]; then
+            echo "======================= GRADLE FAILURE ======================="
+            grep -n -A 25 "What went wrong" /tmp/gradle.log || true
+            grep -n -A 3 "FAILURE:" /tmp/gradle.log || true
+            echo "=============================================================="
+            exit 1
+          fi
           echo "APK(s):"; find app/build/outputs -name "*.apk"
+          test -n "$(find app/build/outputs -name '*.apk' -print -quit)" || { echo "ERROR: no APK produced"; exit 1; }
     artifacts:
       - mobile/android/app/build/outputs/**/*.apk
     # Download the APK from the build page. To get it emailed like TestFlight, add a `publishing.email` block