feat(interaction): 接通叙事/拾取通知Widget表现层

P-016: 将EffectManager的ShowNarrative/HideNarrative/ShowPickupNotification
从日志占位改为真实CreateWidget+AddToViewport+淡入淡出生命周期。

- 新增UPickupNotificationWidget C++基类(对称NarrativeTextWidget)
- EffectManager新增SetWidgetClasses注入接口与Widget弱引用缓存
- PerformCleanup补齐Narrative/Pickup Widget兜底淡出移除
- ASystemDriver新增两个TSubclassOf配置点,BeginPlay注入给EffectManager
- Widget Class未注入时回退日志占位,保证Effect流程不卡

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Source/ChildHood/Interaction/PickupNotificationWidget.cpp

@@ -0,0 +1,57 @@
+// ChildHood Project - 拾取通知 UI 基类 实现
+
+#include "Interaction/PickupNotificationWidget.h"
+#include "Components/TextBlock.h"
+
+void UPickupNotificationWidget::NativeOnInitialized()
+{
+	Super::NativeOnInitialized();
+
+	// 初始隐藏
+	SetVisibility(ESlateVisibility::Hidden);
+}
+
+void UPickupNotificationWidget::SetPickupText(const FString& Text)
+{
+	if (PickupTextBlock)
+	{
+		PickupTextBlock->SetText(FText::FromString(Text));
+	}
+}
+
+void UPickupNotificationWidget::Show()
+{
+	if (bIsVisible) return;
+	bIsVisible = true;
+
+	SetVisibility(ESlateVisibility::HitTestInvisible);
+
+	if (FadeInAnim)
+	{
+		PlayAnimation(FadeInAnim, 0.0f, 1, EUMGSequencePlayMode::Forward, 1.0f);
+	}
+}
+
+void UPickupNotificationWidget::Hide()
+{
+	if (!bIsVisible) return;
+
+	if (FadeOutAnim)
+	{
+		PlayAnimation(FadeOutAnim, 0.0f, 1, EUMGSequencePlayMode::Forward, 1.0f);
+		FTimerHandle TempHandle;
+		if (UWorld* World = GetWorld())
+		{
+			World->GetTimerManager().SetTimer(TempHandle, [this]()
+			{
+				bIsVisible = false;
+				SetVisibility(ESlateVisibility::Hidden);
+			}, 0.2f, false);
+		}
+	}
+	else
+	{
+		bIsVisible = false;
+		SetVisibility(ESlateVisibility::Hidden);
+	}
+}