Add NavigationView support

[Kyle-Ye]

Summary

Add NavigationView support for compatibility with SwiftUI code that still uses the classic navigation container API.

Scope

• Add the public NavigationView container API.
• Support common composition patterns with root content, detail content where applicable, titles, toolbars, and navigation links.
• Integrate with existing navigation preference and toolbar-title plumbing.
• Define supported behavior for single-column and multi-column presentation across platforms.

Acceptance criteria

• A basic NavigationView { ... } compiles and renders.
• Simple NavigationLink navigation works for common destination views.
• Navigation titles/toolbars participate in the expected environment/preference flow.