test infra: JUnit5 unit tests on Android modules + Compose UI test wiring

Add an architecture.android.unit.test convention plugin that runs local unit
tests on the JUnit5 platform via useJUnitPlatform() (AndroidUnitTest extends
Gradle's Test) + the unit-test bundle. Deliberately NOT using the
de.mannodermaus plugin (targets AGP 8.x; we're on AGP 9). Add
junit-platform-launcher (Gradle 9 dropped the bundled launcher); set the
instrumentation runner; add a compose-ui-test bundle pinning espresso/runner to
current versions (transitive espresso 3.5.0 calls the removed
InputManager.getInstance() on API 34+). CI now runs ./gradlew test and compiles
the instrumented tests. Drop unused testing catalog entries.

.github/workflows/ci.yml

@@ -32,5 +32,18 @@ jobs:
       - name: Set up Gradle
         uses: gradle/actions/setup-gradle@v4
 
-      - name: Assemble (debug)
-        run: ./gradlew assembleDebug --no-daemon --stacktrace
+      - name: Unit tests (JUnit 5)
+        run: ./gradlew test --no-daemon --stacktrace
+
+      - name: Assemble (debug) + compile instrumented tests
+        # assembleDebugAndroidTest compiles the Compose UI test; it runs on a device via
+        # connectedDebugAndroidTest (locally / on an emulator runner), not in this build job.
+        run: ./gradlew assembleDebug assembleDebugAndroidTest --no-daemon --stacktrace
+
+      - name: Upload test reports
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: test-reports
+          path: '**/build/reports/tests/'
+          if-no-files-found: ignore