Scaffold native Android build and enforce Rust boundaries (#89)

README.md

@@ -89,6 +89,8 @@ apps/cli        pass-compatible command-line frontend
 apps/tui        Ratatui frontend
 apps/desktop    Iced desktop frontend for macOS, Windows, and Linux
 apple/          iPhone, AutoFill, and watchOS presentation targets
+android/        native Android Compose project
+tools/android-build  Rust-owned Android fixtures and architecture checks
 ```
 
 The Apple project is generated with XcodeGen:
@@ -98,6 +100,9 @@ cd apple
 xcodegen generate
 ```
 
+Android toolchain setup, module boundaries, build gates and simulator updates are
+documented in [`android/README.md`](android/README.md).
+
 Apple App Store metadata, archive verification, submission, and paired iPhone
 and Watch release checks are documented in
 [`apple/AppStore/DISTRIBUTION.md`](apple/AppStore/DISTRIBUTION.md).