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

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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.