Constraint: SRS-163 requires Android back to be handled by the shell/platform layer, and the Dart service existed but was not wired into the live app.
Rejected: Leave BackIntentService test-only and unwired | System back would bypass app policy on Android.
Confidence: medium
Scope-risk: narrow
Directive: Keep back-intent probe state in sync with every new dialog or pushed route added to the Flutter shell.
Tested: dart format apps/chanora_flutter/lib/main.dart; flutter analyze lib/main.dart test/services/back_intent_service_test.dart; flutter test test/services/back_intent_service_test.dart
Not-tested: Manual Android device back-navigation smoke test