fix(ios-qa): generate app-owned bridge accessors deterministically

test/fixtures/ios-qa/FixtureApp/Sources/FixtureApp/FixtureAppState.swift

@@ -1,32 +1,22 @@
-// Canonical app state for the fixture. Every snapshot-eligible field is
-// marked with the @Snapshotable property wrapper that the codegen tool
-// detects via attribute scan.
-//
-// Note: we DON'T use @Observable here because the macro expansion converts
-// stored properties into computed ones, which the @Snapshotable wrapper
-// can't apply to. In production apps that need both observability AND
-// snapshotting, the right pattern is:
-//   - Use ObservableObject + @Published (older API), or
-//   - Hold all @Snapshotable state in a nested struct + replace it
-//     wholesale on restore so SwiftUI sees a single change notification
-//     (the canonical-state-struct atomicity strategy from the plan).
+// Canonical observable app state for the fixture. Snapshot eligibility is a
+// generator-only source marker, not a property wrapper, so it composes with
+// Observation's @Observable macro.
 
 import Foundation
+import Observation
 
-public final class FixtureAppState {
-    @Snapshotable public var isLoggedIn: Bool = false
-    @Snapshotable public var username: String = ""
-    @Snapshotable public var tapCounter: Int = 0
+@Observable
+final class FixtureAppState {
+    // @Snapshotable
+    var isLoggedIn: Bool = false
+    // @Snapshotable
+    var username: String = ""
+    // @Snapshotable
+    var tapCounter: Int = 0
+    // @Snapshotable
+    var nickname: String? = nil
     /// Not snapshotted — ephemeral cache that should never leak via /state/snapshot.
-    public var ephemeralCache: [String: String] = [:]
+    var ephemeralCache: [String: String] = [:]
 
-    public init() {}
-}
-
-/// Property wrapper marker for snapshot-eligible state. The actual wrapper
-/// is a no-op at runtime; codegen-tool detection happens via attribute scan.
-@propertyWrapper
-public struct Snapshotable<Value> {
-    public var wrappedValue: Value
-    public init(wrappedValue: Value) { self.wrappedValue = wrappedValue }
+    init() {}
 }