fix(练习): 修复底部区域布局和焦点问题

- 动态计算底部固定区域高度，避免固定值导致的空白或遮挡
- 底部区域适配侧边栏宽度，不再被左侧菜单遮挡
- 答案隐藏后自动恢复输入框焦点
- 增加辅助信息显示高度（max-h-48）

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

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

src/pages/ProcessPracticePage.tsx

@@ -9,10 +9,14 @@ import {
 import { PracticeMatrix } from '@/components/practice/PracticeMatrix'
 import { InputArea } from '@/components/practice/InputArea'
 import { HintInfo } from '@/components/practice/HintInfo'
+import { useAppStore } from '@/stores/useAppStore'
+import { clsx } from 'clsx'
 
 type CharStatus = 'pending' | 'correct' | 'error'
 
 export default function ProcessPracticePage() {
+  const sidebarOpen = useAppStore((s) => s.sidebarOpen)
+
   // 生成格子顺序
   const [cellSequence] = useState<CellInfo[]>(() => generateCellSequence())
 
@@ -60,6 +64,8 @@ export default function ProcessPracticePage() {
   } | null>(null)
   const [inputLocked, setInputLocked] = useState(false)
   const latestInputRef = useRef<string[]>([])
+  const bottomAreaRef = useRef<HTMLDivElement>(null)
+  const [bottomHeight, setBottomHeight] = useState(0)
 
   // 初始化输入框
   useEffect(() => {
@@ -90,6 +96,19 @@ export default function ProcessPracticePage() {
     }
   }, [answeredCells, currentCellId])
 
+  // 动态计算底部固定区域高度
+  useEffect(() => {
+    const updateBottomHeight = () => {
+      if (bottomAreaRef.current) {
+        setBottomHeight(bottomAreaRef.current.offsetHeight)
+      }
+    }
+
+    updateBottomHeight()
+    window.addEventListener('resize', updateBottomHeight)
+    return () => window.removeEventListener('resize', updateBottomHeight)
+  }, [userInput.length]) // 当输入框数量变化时重新计算
+
   // 切换到指定格子
   const switchToCell = useCallback(
     (cell: CellInfo) => {
@@ -251,6 +270,14 @@ export default function ProcessPracticePage() {
       setShowAnswerForCell(null)
       setInputLocked(false)
       announceToScreenReader('答案已隐藏')
+
+      // 恢复焦点到第一个输入框
+      setTimeout(() => {
+        const firstInput = document.querySelector(
+          '.practice-input-area input'
+        ) as HTMLInputElement
+        firstInput?.focus()
+      }, 100)
     }
   }, [showAnswerForCell])
 
@@ -262,6 +289,14 @@ export default function ProcessPracticePage() {
     if (remainingTime <= 0) {
       setShowAnswerForCell(null)
       setInputLocked(false)
+
+      // 恢复焦点
+      setTimeout(() => {
+        const firstInput = document.querySelector(
+          '.practice-input-area input'
+        ) as HTMLInputElement
+        firstInput?.focus()
+      }, 100)
       return
     }
 
@@ -269,6 +304,14 @@ export default function ProcessPracticePage() {
       setShowAnswerForCell(null)
       setInputLocked(false)
       announceToScreenReader('答案已自动隐藏')
+
+      // 恢复焦点
+      setTimeout(() => {
+        const firstInput = document.querySelector(
+          '.practice-input-area input'
+        ) as HTMLInputElement
+        firstInput?.focus()
+      }, 100)
     }, remainingTime)
 
     return () => clearTimeout(timer)
@@ -362,7 +405,7 @@ export default function ProcessPracticePage() {
       </div>
 
       {/* 主内容区域 */}
-      <div className="pb-80">
+      <div style={{ paddingBottom: `${bottomHeight}px` }}>
         {/* 矩阵区域 */}
         <div className="max-w-7xl mx-auto py-4">
           <PracticeMatrix
@@ -378,35 +421,44 @@ export default function ProcessPracticePage() {
       </div>
 
       {/* 底部固定区域 */}
-      <div className="fixed bottom-0 left-0 right-0 bg-white/60 dark:bg-gray-800/60 backdrop-blur-md border-t border-gray-200 dark:border-gray-700 z-10">
+      <div
+        ref={bottomAreaRef}
+        className={clsx(
+          'fixed bottom-0 left-0 right-0 bg-white/60 dark:bg-gray-800/60 backdrop-blur-md border-t border-gray-200 dark:border-gray-700 z-10 transition-all duration-300',
+          sidebarOpen ? 'lg:ml-64' : 'lg:ml-20'
+        )}
+      >
         <div className="max-w-7xl mx-auto">
           {/* 输入区域 */}
           <div className="py-4 border-b border-gray-200/50 dark:border-gray-700/50">
-            <InputArea
-              userInput={userInput}
-              charStatuses={charStatuses}
-              isComposing={isComposing}
-              inputLocked={inputLocked}
-              lastErrorTimestamp={lastErrorTimestamp}
-              onInputChange={handleInputChange}
-              onCompositionStart={handleCompositionStart}
-              onCompositionEnd={handleCompositionEnd}
-              onPaste={handlePaste}
-            />
+            <div className="flex items-center justify-center gap-3">
+              <InputArea
+                userInput={userInput}
+                charStatuses={charStatuses}
+                isComposing={isComposing}
+                inputLocked={inputLocked}
+                lastErrorTimestamp={lastErrorTimestamp}
+                onInputChange={handleInputChange}
+                onCompositionStart={handleCompositionStart}
+                onCompositionEnd={handleCompositionEnd}
+                onPaste={handlePaste}
+              />
 
-            {/* 提示按钮 */}
-            <div className="flex justify-center mt-3">
+              {/* 查看答案按钮 */}
               <button
                 onClick={() => currentCellId && handleLongPress(currentCellId)}
-                className="px-4 py-1.5 text-sm text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-gray-100 transition-colors"
+                className="p-2 text-gray-500 dark:text-gray-400 hover:text-blue-600 dark:hover:text-blue-400 transition-colors"
+                title="查看答案（长按格子也可以）"
               >
-                想不起来？长按格子或点击此处查看答案
+                <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
+                </svg>
               </button>
             </div>
           </div>
 
           {/* 辅助信息区域 */}
-          <div className="py-3 px-4 max-h-40 overflow-y-auto">
+          <div className="py-3 px-4 max-h-48 overflow-y-auto">
             <HintInfo currentCell={currentCell} />
           </div>
         </div>