学习模式取消自动检查，改为确认按钮手动提交

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

LearnEnglish/LearnEnglish/Views/QuizViewController.swift

@@ -222,9 +222,10 @@ final class QuizViewController: UIViewController {
             if config.isStudyMode {
                 nextButton.isHidden = true
                 spellingView.onChange = { [weak self] in
-                    guard let self, spellingView.isComplete else { return }
-                    submitSpelling(spellingView.typedWord(), for: question)
+                    guard let self else { return }
+                    spellingView.confirmButton?.isEnabled = spellingView.isComplete
                 }
+                spellingView.confirmButton?.isEnabled = false
             } else {
                 spellingView.onChange = { [weak self] in
                     guard let self else { return }

LearnEnglish/LearnEnglish/Views/SpellingInputView.swift

@@ -3,6 +3,7 @@ import UIKit
 final class SpellingInputView: UIView, UITextFieldDelegate {
     var onChange: (() -> Void)?
     var onSubmit: (() -> Void)?
+    private(set) var confirmButton: UIButton?
 
     private let hiddenField = UITextField()
     private let stack = UIStackView()
@@ -73,6 +74,7 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
             return outgoing
         }
         let glassButton = UIButton(configuration: glassConfig)
+        confirmButton = glassButton
         glassButton.addAction(UIAction { [weak self] _ in
             self?.onSubmit?()
         }, for: .touchUpInside)