arch-mvvm-swiftuilisted

# MVVM (SwiftUI, `@Observable`) **Source references (study after reading this skill):** - Apple Scrumdinger sample — https://developer.apple.com/tutorials/app-dev-training/getting-started-with-scrumdinger - Apple Backyard Birds sample — https://developer.apple.com/documentation/swiftui/backyard-birds-sample - Antoine van der Lee, *MVVM in SwiftUI* — https://www.avanderlee.com/swiftui/mvvm-architectural-coding-pattern-to-structure-views/ - Sarunw, *Observation Framework in iOS 17* — https://sarunw.com/posts/observation-framework-in-ios17/ ## When to use - SwiftUI on iOS 17+. - Medium project, 20–80 screens. - Per-property invalidation needed (perf-sensitive lists, charts). ## Folder structure ``` App/AppEntry.swift Features/ UserList/ UserListView.swift UserListModel.swift UserDetail/ UserDetailView.swift UserDetailModel.swift Domain/User.swift Domain/UserRepository.swift Data/LiveUserRepository.swift ``` ## Reference implementation The full worked `UserList + UserDetail` feature lives in **`examples/mvvm-swiftui/`** — `@Observable @MainActor` models, SwiftUI Views, the app entry point, and model XCTest. `Domain` + `Data` + test fakes follow `skills/REFERENCE_FEATURE.md` (vendored per example). Key things to notice: - **The model is `@Observable @MainActor`**, owned by the View via `@State` and injected into child views as a plain property — no `ObservableObject`/`@Published`. - **Paging, refresh, and error state live in the model**, exposed as `pri