Refactor: Replace RenderNotifier.current global with dependency injection

- Make RenderNotifier.current optional (nil by default) to support DI
- Add RenderNotifierKey and renderNotifier property to EnvironmentValues
- Initialize renderNotifier in RenderLoop.buildEnvironment()
- Migrate Spinner animation loop to read from environment
- Migrate NotificationHostModifier to read from environment via parameter
- Update StateBox.didSet to use optional chaining fallback
- Update AppStorage.wrappedValue setter to use optional chaining fallback
- Update NotificationService.post() to use optional chaining fallback
- Update test comments to reflect optional chaining pattern
- All 1069 tests pass, no new compiler warnings

Phase 3 implementation of P4.16 dependency injection refactor complete.

Sources/TUIkit/App/RenderLoop.swift

@@ -351,6 +351,7 @@ extension RenderLoop {
         environment.keyEventDispatcher = tuiContext.keyEventDispatcher
         environment.renderCache = tuiContext.renderCache
         environment.preferenceStorage = tuiContext.preferences
+        environment.renderNotifier = RenderNotifier.current
 
         return environment
     }

Sources/TUIkit/Environment/ServiceEnvironment.swift

@@ -4,6 +4,14 @@
 //  Created by LAYERED.work
 //  License: MIT
 
+// MARK: - Render Notifier (AppState)
+
+/// EnvironmentKey for the AppState reference used to trigger re-renders.
+/// Render-time consumers (Spinner, NotificationHostModifier) read from here.
+private struct RenderNotifierKey: EnvironmentKey {
+    static let defaultValue: AppState? = nil
+}
+
 // MARK: - Lifecycle Manager
 
 /// EnvironmentKey for view lifecycle tracking (appear/disappear/task).
@@ -57,6 +65,13 @@ private struct ActiveFocusSectionKey: EnvironmentKey {
 
 extension EnvironmentValues {
 
+    /// The AppState reference for triggering re-renders.
+    /// Used by render-time consumers (Spinner, NotificationHostModifier) to signal render needs.
+    var renderNotifier: AppState? {
+        get { self[RenderNotifierKey.self] }
+        set { self[RenderNotifierKey.self] = newValue }
+    }
+
     /// View lifecycle tracking (appear, disappear, task management).
     var lifecycle: LifecycleManager? {
         get { self[LifecycleKey.self] }

Sources/TUIkit/Notification/NotificationHostModifier.swift

@@ -54,7 +54,8 @@ extension NotificationHostModifier: Renderable {
         // Start the animation timer if not already running.
         startAnimationTask(
             entries: activeEntries,
-            lifecycle: context.environment.lifecycle!
+            lifecycle: context.environment.lifecycle!,
+            renderNotifier: context.environment.renderNotifier
         )
 
         let now = Date().timeIntervalSinceReferenceDate
@@ -149,7 +150,8 @@ private extension NotificationHostModifier {
     /// The task stops automatically when no notifications are active.
     func startAnimationTask(
         entries: [NotificationEntry],
-        lifecycle: LifecycleManager
+        lifecycle: LifecycleManager,
+        renderNotifier: AppState?
     ) {
         let token = "notification-host-animation"
 
@@ -171,12 +173,12 @@ private extension NotificationHostModifier {
                 }
                 try? await Task.sleep(nanoseconds: triggerNanos)
                 guard !Task.isCancelled else { break }
-                RenderNotifier.current.setNeedsRender()
+                renderNotifier?.setNeedsRender()
             }
 
             // Final render to clear expired notifications.
             lifecycle.resetAppearance(token: token)
-            RenderNotifier.current.setNeedsRender()
+            renderNotifier?.setNeedsRender()
         }
     }
 }

Sources/TUIkit/Notification/NotificationService.swift

@@ -115,7 +115,8 @@ extension NotificationService {
         lock.lock()
         entries.append(entry)
         lock.unlock()
-        RenderNotifier.current.setNeedsRender()
+        // Property wrapper setters lack render context, so fall back to global
+        RenderNotifier.current?.setNeedsRender()
     }
 
     /// Returns a snapshot of all currently active notifications.

Sources/TUIkit/State/AppStorage.swift

@@ -281,7 +281,8 @@ public struct AppStorage<Value: Codable>: @unchecked Sendable {
         }
         nonmutating set {
             storage.setValue(newValue, forKey: key)
-            RenderNotifier.current.setNeedsRender()
+            // Property wrapper setters lack render context, so fall back to global
+            RenderNotifier.current?.setNeedsRender()
         }
     }
 

Sources/TUIkit/Views/Spinner.swift

@@ -283,11 +283,12 @@ private struct _SpinnerCore: View, Renderable {
             _ = lifecycle.recordAppear(token: token) {}
 
             let triggerNanos: UInt64 = 28_000_000  // 28ms — matches run loop poll rate (~35 FPS)
+            let renderNotifier = context.environment.renderNotifier
             lifecycle.startTask(token: token, priority: .medium) {
                 while !Task.isCancelled {
                     try? await Task.sleep(nanoseconds: triggerNanos)
                     guard !Task.isCancelled else { break }
-                    RenderNotifier.current.setNeedsRender()
+                    renderNotifier?.setNeedsRender()
                 }
             }
         } else {

Sources/TUIkitView/State/State.swift

@@ -141,7 +141,9 @@ public enum RenderNotifier {
     /// No concurrent access is possible: they are initialized once and then
     /// read/written only during rendering.
     ///
-    public nonisolated(unsafe) static var current = AppState()
+    /// Optional fallback for property wrapper setters that lack render context.
+    /// Render-time consumers should read from EnvironmentValues.renderNotifier instead.
+    public nonisolated(unsafe) static var current: AppState?
 
     /// The active render cache for subtree memoization.
     ///

Sources/TUIkitView/State/StateStorage.swift

@@ -158,7 +158,8 @@ public final class StateBox<Value>: @unchecked Sendable {
             } else {
                 RenderNotifier.renderCache?.clearAll()
             }
-            RenderNotifier.current.setNeedsRender()
+            // Property wrapper setters lack render context, so fall back to global
+            RenderNotifier.current?.setNeedsRender()
         }
     }
 

Tests/TUIkitTests/StatePropertyTests.swift

@@ -30,7 +30,7 @@ struct StatePropertyWrapperTests {
 
     @Test("State mutation triggers render via RenderNotifier")
     func stateTriggerRender() {
-        // StateBox.didSet calls RenderNotifier.current.setNeedsRender().
+        // StateBox.didSet calls RenderNotifier.current?.setNeedsRender() (optional chaining).
         // We swap in a fresh AppState, mutate, and check immediately.
         // This is a single-expression sequence with no yield points,
         // so no parallel test can interfere between set and check.