fix(练习): 修复中文输入法和字符验证问题

- 移除 input maxLength 限制，支持输入法多字符输入
- 使用 ref 保存最新输入状态，避免闭包导致的状态滞后
- 重构验证逻辑，修复字符对比错误（对比原始答案而非标准化答案）
- 修复输入法确认后验证使用旧数据的问题

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <noreply@hapi.run>

src/components/practice/InputArea.tsx

@@ -134,7 +134,6 @@ export function InputArea({
                   !isComposing && isError && 'border-red-500',
                   inputLocked && 'cursor-not-allowed opacity-50'
                 )}
-                maxLength={1}
                 autoComplete="off"
                 autoCorrect="off"
                 autoCapitalize="off"

src/pages/ProcessPracticePage.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect, useCallback } from 'react'
+import { useState, useEffect, useCallback, useRef } from 'react'
 import { motion } from 'framer-motion'
 import {
   generateCellSequence,
@@ -39,6 +39,7 @@ export default function ProcessPracticePage() {
     expiresAt: number
   } | null>(null)
   const [inputLocked, setInputLocked] = useState(false)
+  const latestInputRef = useRef<string[]>([])
 
   // 初始化输入框
   useEffect(() => {
@@ -49,6 +50,11 @@ export default function ProcessPracticePage() {
     }
   }, [currentCellId, cellSequence])
 
+  // 同步当前输入快照，供输入法确认后复用
+  useEffect(() => {
+    latestInputRef.current = userInput
+  }, [userInput])
+
   // 切换到指定格子
   const switchToCell = useCallback(
     (cell: CellInfo) => {
@@ -94,55 +100,57 @@ export default function ProcessPracticePage() {
     switchToCell(prevCell)
   }, [currentCellId, cellSequence, switchToCell])
 
-  // 输入验证
-  const handleInputChange = useCallback(
-    (newInput: string[]) => {
-      setUserInput(newInput)
-
-      // 等待输入法确认后再验证
-      if (isComposing) return
-
+  // 统一的输入验证逻辑
+  const validateInput = useCallback(
+    (input: string[]) => {
       const currentCell = cellSequence.find((c) => c.id === currentCellId)
       if (!currentCell || !currentCellId) return
 
-      // 使用原始答案长度渲染横线，使用标准化答案验证
       const originalAnswer = currentCell.answer
       const normalizedInput = normalizeAnswer(
-        newInput.join(''),
+        input.join(''),
         currentCell.type === 'knowledge-area'
       )
       const normalizedAnswer = currentCell.normalizedAnswer
+      const normalizeChar = (char: string) =>
+        normalizeAnswer(char, false) || char
 
-      // 逐字符验证状态（基于原始答案）
-      const newCharStatuses = newInput.map((char, i) => {
+      const newCharStatuses = input.map((char, i) => {
         if (!char) return 'pending' as CharStatus
-        // 对比时使用标准化后的字符
-        const normalizedChar = normalizeAnswer(char, false)
-        const expectedChar = normalizedAnswer[i]
-        return normalizedChar === expectedChar
+        const expectedChar = originalAnswer[i] || ''
+        if (!expectedChar) return 'error' as CharStatus
+        return normalizeChar(char) === normalizeChar(expectedChar)
           ? ('correct' as CharStatus)
           : ('error' as CharStatus)
       })
       setCharStatuses(newCharStatuses)
 
-      // 完整答案验证
       const isComplete =
-        newInput.every((c) => c !== '') &&
-        newInput.length === originalAnswer.length
+        input.every((c) => c !== '') && input.length === originalAnswer.length
       const isCorrect = isComplete && normalizedInput === normalizedAnswer
 
       if (isCorrect) {
-        // 答对：标记格子，延迟跳转（给用户反馈时间）
         setAnsweredCells((prev) => new Map(prev).set(currentCellId, true))
         setTimeout(() => {
           moveToNextCell()
         }, 300)
       } else if (isComplete) {
-        // 答错：记录错误时间戳，触发红线动画
         setLastErrorTimestamp(Date.now())
       }
     },
-    [isComposing, currentCellId, cellSequence, moveToNextCell]
+    [cellSequence, currentCellId, moveToNextCell]
+  )
+
+  const handleInputChange = useCallback(
+    (newInput: string[]) => {
+      latestInputRef.current = newInput
+      setUserInput(newInput)
+
+      if (isComposing) return
+
+      validateInput(newInput)
+    },
+    [isComposing, validateInput]
   )
 
   // 输入法状态管理
@@ -152,11 +160,11 @@ export default function ProcessPracticePage() {
 
   const handleCompositionEnd = useCallback(() => {
     setIsComposing(false)
-    // 输入法确认后立即验证（使用当前完整输入）
+    // 输入法确认后根据最新快照重新验证
     requestAnimationFrame(() => {
-      handleInputChange(userInput)
+      validateInput(latestInputRef.current)
     })
-  }, [userInput, handleInputChange])
+  }, [validateInput])
 
   // 批量粘贴处理
   const handlePaste = useCallback(