Docs: AAB build steps + Play Billing testing checklist

ARCHITECTURE.md

@@ -218,6 +218,14 @@ Pattern implementations should be strategy-based, for example:
 ## 11. Safety Architecture
 
 Safety checks should exist in more than one place:
+
+---
+
+## Development notes
+
+Build/release steps (AAB) and Play Billing testing checklist live in:
+
+- `DEVELOPMENT.md`
 - onboarding acknowledgment,
 - pre-session checks,
 - runtime interruption handling,