feat(domain): add SidebarSection grouping and sidebar localization strings

Add SidebarSection enum to AtlasRoute with core/manage groupings,
isSidebarRoute filter, and sidebarSection lookup. Add en/zh-Hans
strings for sidebar sections, about window title, and about command.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Packages/AtlasDomain/Sources/AtlasDomain/AtlasDomain.swift

@@ -11,6 +11,57 @@ public enum AtlasRoute: String, CaseIterable, Codable, Hashable, Identifiable, S
 
     public var id: String { rawValue }
 
+    // MARK: - Sidebar
+
+    public enum SidebarSection: String, CaseIterable, Identifiable, Sendable {
+        case core
+        case manage
+
+        public var id: String { rawValue }
+
+        public var title: String {
+            switch self {
+            case .core:
+                return AtlasL10n.string("sidebar.section.core")
+            case .manage:
+                return AtlasL10n.string("sidebar.section.manage")
+            }
+        }
+
+        public var routes: [AtlasRoute] {
+            switch self {
+            case .core:
+                return [.overview, .smartClean, .apps]
+            case .manage:
+                return [.history, .permissions]
+            }
+        }
+    }
+
+    public var isSidebarRoute: Bool {
+        switch self {
+        case .settings, .about:
+            return false
+        default:
+            return true
+        }
+    }
+
+    public static var sidebarRoutes: [AtlasRoute] {
+        allCases.filter(\.isSidebarRoute)
+    }
+
+    public var sidebarSection: SidebarSection? {
+        switch self {
+        case .overview, .smartClean, .apps:
+            return .core
+        case .history, .permissions:
+            return .manage
+        case .settings, .about:
+            return nil
+        }
+    }
+
     public var title: String {
         switch self {
         case .overview:

Packages/AtlasDomain/Sources/AtlasDomain/Resources/en.lproj/Localizable.strings

@@ -602,3 +602,8 @@
 "about.social.discord" = "Discord";
 
 "smartclean.preview.callout.review.title" = "Some steps in this plan need a closer review";
+
+"sidebar.section.core" = "Core";
+"sidebar.section.manage" = "Manage";
+"about.window.title" = "About Atlas";
+"commands.about" = "About Atlas";

Packages/AtlasDomain/Sources/AtlasDomain/Resources/zh-Hans.lproj/Localizable.strings

@@ -602,3 +602,8 @@
 "about.social.discord" = "Discord";
 
 "smartclean.preview.callout.review.title" = "这份计划中仍有步骤需要复核";
+
+"sidebar.section.core" = "核心";
+"sidebar.section.manage" = "管理";
+"about.window.title" = "关于 Atlas";
+"commands.about" = "关于 Atlas";