[Infra] App Coordinator 생성, RootView 설정

Projects/App/Sources/ThreeDaysApp.swift

@@ -1,11 +1,49 @@
 import SwiftUI
+import DesignCore
 import DesignPreview
+import CoreKit
+import Main
 
 @main
 struct ThreeDaysApp: App {
+    let coordinator = AppCoordinator.shared
+
     var body: some Scene {
         WindowGroup {
+            ZStack(alignment: .bottomLeading) {
+                rootView
+                #if DEBUG
+                debugMenuPicker
+                    .padding(.leading, 16)
+                    .padding(.bottom, 16)
+                #endif
+            }
+        }
+    }
+
+    @ViewBuilder
+    var rootView: some View {
+        switch coordinator.rootView {
+        case .designPreview:
             DesignPreviewView()
+        case .main:
+            MainView()
+        }
+    }
+
+    #if DEBUG
+    @ViewBuilder
+    var debugMenuPicker: some View {
+        Menu("🚀 개발모드") {
+            ForEach(FeatureType.allCases, id: \.self) { feature in
+                Button(feature.name) {
+                    coordinator.changeRootView(feature)
+                }
+            }
         }
+        .buttonStyle(BorderedProminentButtonStyle())
+        .typography(.semibold_14)
+        .tint(DesignCore.grey300)
     }
+    #endif
 }

Projects/Core/CoreKit/Sources/AppCoordinator.swift

@@ -0,0 +1,23 @@
+//
+//  AppCoordinator.swift
+//  CoreKit
+//
+//  Created by 김지수 on 9/18/24.
+//  Copyright © 2024 com.weave. All rights reserved.
+//
+
+import SwiftUI
+
+@Observable public final class AppCoordinator {
+    //MARK: - Lifecycle
+    public static var shared = AppCoordinator()
+    private init() {}
+
+    //MARK: - Properties
+    public private(set) var rootView = FeatureType.designPreview
+
+    //MARK: - Methods
+    public func changeRootView(_ feature: FeatureType) {
+        rootView = feature
+    }
+}

Projects/Core/CoreKit/Sources/FeatureTypes.swift

@@ -0,0 +1,21 @@
+//
+//  FeatureTypes.swift
+//  CoreKit
+//
+//  Created by 김지수 on 9/18/24.
+//  Copyright © 2024 com.weave. All rights reserved.
+//
+
+import Foundation
+
+public enum FeatureType: CaseIterable {
+    case designPreview
+    case main
+
+    public var name: String {
+        switch self {
+        case .designPreview: return "Design Preview"
+        case .main: return "메인"
+        }
+    }
+}