有子分类的类别改为面板入口，点击后进入子分类列表页再进入单词列表

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

LearnEnglish/LearnEnglish/Views/CategoryListViewController.swift

@@ -53,7 +53,12 @@ final class CategoryListViewController: UITableViewController {
     override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
         Haptics.selection()
         let category = store.categories[indexPath.row]
-        navigationController?.pushViewController(
+        if let subs = category.subcategories, !subs.isEmpty {
-            WordListViewController(category: category, colorIndex: indexPath.row), animated: true)
+            let vc = SubcategoryListViewController(category: category, colorIndex: indexPath.row)
+            navigationController?.pushViewController(vc, animated: true)
+        } else {
+            navigationController?.pushViewController(
+                WordListViewController(category: category, colorIndex: indexPath.row), animated: true)
+        }
     }
 }

LearnEnglish/LearnEnglish/Views/SubcategoryListViewController.swift

@@ -0,0 +1,50 @@
+import UIKit
+
+final class SubcategoryListViewController: UITableViewController {
+    private let category: WordCategory
+    private let colorIndex: Int
+    private let subcategories: [Subcategory]
+
+    init(category: WordCategory, colorIndex: Int) {
+        self.category = category
+        self.colorIndex = colorIndex
+        self.subcategories = category.subcategories ?? []
+        super.init(style: .plain)
+    }
+
+    @available(*, unavailable)
+    required init?(coder: NSCoder) { fatalError() }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        title = category.name
+        navigationItem.largeTitleDisplayMode = .never
+        tableView.register(CategoryCardCell.self, forCellReuseIdentifier: "cell")
+        tableView.separatorStyle = .none
+        tableView.backgroundColor = .systemBackground
+        tableView.contentInset.top = 8
+    }
+
+    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+        subcategories.count
+    }
+
+    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
+        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! CategoryCardCell
+        let sub = subcategories[indexPath.row]
+        cell.configure(with: makeSynthetic(sub), color: Theme.Color.category(at: colorIndex))
+        return cell
+    }
+
+    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
+        Haptics.selection()
+        let sub = subcategories[indexPath.row]
+        navigationController?.pushViewController(
+            WordListViewController(category: makeSynthetic(sub), colorIndex: colorIndex), animated: true)
+    }
+
+    private func makeSynthetic(_ sub: Subcategory) -> WordCategory {
+        WordCategory(id: sub.name, name: sub.name, icon: category.icon,
+                     words: sub.words, subcategories: nil)
+    }
+}