ci: speed up the android build with one debug-scoped gradle invocation

The build job ran assembleDebug, test, and lint as three separate ./gradlew
invocations (three configuration phases), and test/lint each built BOTH the
debug and release variants. CI ships the debug APK and the release variant's
compilation is validated by the release job's assembleRelease, so the debug
variant is sufficient on the build job.

Collapse to a single debug-scoped invocation:
  ./gradlew assembleDebug testDebugUnitTest lintDebug

Keeps every debug unit test, debug lint check, and the APK packaging check;
drops only the redundant release-variant unit tests + release lint and two
extra configuration phases. ~2 min faster on a ~9 min build (unit tests
146s->~75s, lint 61s->~30s, two fewer daemon/config startups). No tests
removed.

Author: vitofico

.github/workflows/android-ci.yaml

@@ -160,12 +160,13 @@ jobs:
             echo "::error::Rename guard found un-allowlisted OPDS_SYNC / opds-sync / opds_sync references."
             exit 1
           fi
-      - name: Assemble debug APK
-        run: ./gradlew assembleDebug --stacktrace
-      - name: Unit tests
-        run: ./gradlew test --stacktrace
-      - name: Lint
-        run: ./gradlew lint --stacktrace
+      # One Gradle invocation (shared configuration phase + daemon) scoped to the
+      # debug variant. `test`/`lint` build BOTH debug and release variants; CI
+      # ships the debug APK and the release variant's compilation is validated by
+      # the release job's assembleRelease, so the debug variant is sufficient
+      # here. Cuts the build ~2 min without dropping any debug test or lint check.
+      - name: Build, unit-test & lint (debug)
+        run: ./gradlew assembleDebug testDebugUnitTest lintDebug --stacktrace
       - name: Upload debug APK
         if: github.ref == 'refs/heads/main'
         uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5