任务说明补齐 23 份；设计器支持窗体改名

- 其余 21 个实验的 task.md：控件名照示例代码，"在平台上怎么试"和评分步骤一致，列出书上的印刷错误和控件名不一致
- 窗体改名：属性窗口里选中窗体可以改名称，类名、构造函数、new X()、Program.cs 和两个文件名一起改；方法名和字符串不变
- 11 个主窗体不叫 Form1 的实验，任务说明提示先改窗体名再双击生成 Load 事件
- 测试：表头只认分隔行上面那一行，数据行里出现"名称"不再被当成表头

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/test/samples.test.ts

@@ -6,15 +6,18 @@ import { listSamples, loadSample, loadTask } from '../src/samples'
 function tableNames(task: string): string[] {
   const names: string[] = []
   let column = -1
+  let previous: string[] = []
   for (const line of task.split('\n')) {
     if (!line.trim().startsWith('|')) {
       column = -1
+      previous = []
       continue
     }
     const cells = line.trim().replace(/^\||\|$/g, '').split('|')
-    const header = cells.findIndex((c) => c.includes('名称'))
-    if (header >= 0) column = header
+    // 表头是分隔行（|---|）上面那一行；数据行里出现"名称"两个字不算表头
+    if (cells.every((c) => /^\s*:?-+:?\s*$/.test(c))) column = previous.findIndex((c) => c.includes('名称'))
     else if (column >= 0) names.push(...[...(cells[column] ?? '').matchAll(/`([^`]+)`/g)].map((m) => m[1]))
+    previous = cells
   }
   return names
 }