Share a capability between features

Bookmarks and Insights demonstrate the three-layer model with ordinary Flutter widgets. The app chooses a memory plugin. Both feature descriptors contribute their own routes, and their screens consume the shared contract.

How the pieces fit together

The complete walkthrough includes setup, runnable code, ownership, and package extraction. The checked-out example lives in vyuh_core/example/composed_app.dart and is synchronized into the documentation from source.

Use this example to see:

• App-owned selection through PluginDescriptor.others.
• Feature-owned routes through FeatureDescriptor.
• Contract lookup with getPlugin<BookmarksPlugin>() after initialization.
• Shared data observed with Flutter's ValueListenableBuilder.
• Cleanup owned by the plugin and widget layers that created the resources.

The memory adapter retains entries for one platform lifecycle. A persistence adapter needs an explicit loading/error contract if its operations are asynchronous. Companion links are app-supplied, so Insights can also run in an app that omits the Bookmarks feature.