feat: integrate pixel teacher presence and resilient classroom preview

electron/coding-teacher/context.ts

@@ -61,8 +61,10 @@ export function compileTeacherContext(
     ].join('\n\n'),
   };
   const current: TeacherModelMessage = {
-    role: 'user',
-    content: [
+    role: intent === 'check-in' ? 'system' : 'user',
+    content: intent === 'check-in'
+      ? '本轮是老师定时主动关心，不是学生提问。依据来源操作对话中已完成的文字和老师咨询历史，自然地说一段简短中文关心、具体建议或思考引导，约 120 字，最多问一个问题，不要求学生立即回答。只围绕已有证据，不重复刚说过的内容，不整理待办、不替学生作决定；没有实际看到或操作作品，不能假装看到了画面、运行或试玩过作品。直接说给学生听，不提定时检查、系统触发等技术过程。'
+      : [
       ...references.map(
         (ref) =>
           '明确引用' +
@@ -97,13 +99,13 @@ export function compileTeacherContext(
           },
         ]
       : []),
-    ...exchanges.flatMap((request) => [
-      {
+    ...exchanges.flatMap((request): TeacherModelMessage[] => [
+      ...(request.intent === 'check-in' ? [] : [{
         role: 'user' as const,
         content: [...request.references.map((ref) => '明确引用：\n' + ref.text), request.text].join(
           '\n\n'
         ),
-      },
+      }]),
       {
         role: 'assistant' as const,
         content: [
@@ -121,8 +123,7 @@ export function compileTeacherContext(
     omitted++;
   }
   while (estimateTeacherTokens(build()) > maxInputTokens && exchanges.length > 1) {
-    exchanges.shift();
-    omitted += 2;
+    omitted += exchanges.shift()?.intent === 'check-in' ? 1 : 2;
   }
   const messages = build();
   if (estimateTeacherTokens(messages) > maxInputTokens)