拼写改为确认按钮手动提交，点击已填字母可删除重输

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

LearnEnglish/LearnEnglish/Views/QuizViewController.swift

@@ -89,7 +89,7 @@ final class QuizViewController: UIViewController {
         var nextConfig = UIButton.Configuration.borderedProminent()
         nextConfig.contentInsets = .init(top: 12, leading: 16, bottom: 12, trailing: 16)
         nextButton.configuration = nextConfig
-        nextButton.addAction(UIAction { [weak self] _ in self?.next() }, for: .touchUpInside)
+        nextButton.addAction(UIAction { [weak self] _ in self?.primaryButtonTapped() }, for: .touchUpInside)
 
         let headerStack = UIStackView(arrangedSubviews: [progressView, countLabel])
         headerStack.axis = .vertical
@@ -136,7 +136,6 @@ final class QuizViewController: UIViewController {
 
         resultLabel.isHidden = true
         resultPhoneticLabel.isHidden = true
-        nextButton.isHidden = true
 
         let isSpelling = config.mode == .spelling
         optionsStack.isHidden = isSpelling
@@ -146,11 +145,16 @@ final class QuizViewController: UIViewController {
         if isSpelling {
             spellingHintLabel.text = "\(question.word.word.count) 个字母，补全空缺部分"
             spellingView.configure(blankedWord: question.blankedWord, blankPositions: question.blankPositions)
-            spellingView.onComplete = { [weak self] typed in
-                self?.submitSpelling(typed, for: question)
+            spellingView.onChange = { [weak self] in
+                guard let self else { return }
+                nextButton.isEnabled = spellingView.isComplete
             }
+            nextButton.configuration?.title = "确认"
+            nextButton.isEnabled = false
+            nextButton.isHidden = false
             spellingView.activate()
         } else {
+            nextButton.isHidden = true
             buildOptionButtons(for: question)
         }
     }
@@ -221,9 +225,19 @@ final class QuizViewController: UIViewController {
         resultLabel.isHidden = false
 
         nextButton.configuration?.title = currentIndex + 1 < questions.count ? "下一题" : "查看成绩"
+        nextButton.isEnabled = true
         nextButton.isHidden = false
     }
 
+    private func primaryButtonTapped() {
+        if config.mode == .spelling, selectedOption == nil {
+            guard let question = current, spellingView.isComplete else { return }
+            submitSpelling(spellingView.typedWord(), for: question)
+        } else {
+            next()
+        }
+    }
+
     private func next() {
         if currentIndex + 1 < questions.count {
             currentIndex += 1