fix: 修复6个bug并接入CodeStable工作流

Bug修复:
- GetWorkList 使用了错误的 RecordType (RecordStudy→RecordWork)
- AllRecord handler 返回错误的分页信息 (page硬编码1, pageSize用RecordsCount)
- CourseParse creditNode nil panic (加nil检查)
- WebSocket CheckOrigin 安全漏洞 (release模式限制为同源)
- math/rand 可预测 (替换为 crypto/rand)
- GetDiscussList 未实现 (补全实现, 移除重复路由)

其他:
- 接入 CodeStable 工作流体系 (codestable/ 骨架 + AGENTS.md)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/ckwk/api.go

@@ -193,6 +193,7 @@ func (wk *WK) Login() (bool, error) {
 	return true, nil
 }
 
+// parseLoginResp: 解析登录响应
 func (wk *WK) parseLoginResp(body []byte) (LoginResp, error) {
 	var result LoginResp
 	if len(body) == 0 {
@@ -273,12 +274,14 @@ func (wk *WK) CourseParse(content string) ([]Course, error) {
 
 		var credit float32
 		creditNode := htmlquery.FindOne(node, `.//div[@class="note"]/div[@class="number"]/span`)
-		creditStr := strings.TrimSpace(htmlquery.InnerText(creditNode))
-		creditVal, err := strconv.ParseFloat(creditStr, 32)
-		if err == nil {
-			credit = float32(creditVal)
-		} else {
-			log.Warn("课程学分转换失败", zap.Error(err))
+		if creditNode != nil {
+			creditStr := strings.TrimSpace(htmlquery.InnerText(creditNode))
+			creditVal, err := strconv.ParseFloat(creditStr, 32)
+			if err == nil {
+				credit = float32(creditVal)
+			} else {
+				log.Warn("课程学分转换失败", zap.Error(err))
+			}
 		}
 
 		typeNode := htmlquery.FindOne(node, `.//div[@class="note"]/div[@class="kind"]/span`)
@@ -352,6 +355,11 @@ func (wk *WK) UserInfoParse(content string) (User, error) {
 	return user, nil
 }
 
+// QuestionAnswerParse: 解析题目答案
+func (wk *WK) QuestionAnswerParse(content string) (string, error) {
+	return "", nil
+}
+
 // UserGet: 用户信息获取
 func (wk *WK) UserInfoGet() (User, error) {
 	var user User
@@ -467,10 +475,9 @@ func (wk *WK) GetStudyList(courseID, page string) (*AllRecordResp[StudyList], er
 	return GetRecords[StudyList](wk, RecordStudy, courseID, page)
 }
 
-// GetExamList: 获取作业记录
-// todo
-func (wk *WK) GetWorkList(courseID, page string) (*AllRecordResp[ExamList], error) {
-	return GetRecords[ExamList](wk, RecordStudy, courseID, page)
+// GetWorkList: 获取作业记录
+func (wk *WK) GetWorkList(courseID, page string) (*AllRecordResp[WorkList], error) {
+	return GetRecords[WorkList](wk, RecordWork, courseID, page)
 }
 
 // GetExamList: 获取考试记录
@@ -478,10 +485,9 @@ func (wk *WK) GetExamList(courseID, page string) (*AllRecordResp[ExamList], erro
 	return GetRecords[ExamList](wk, RecordExam, courseID, page)
 }
 
-// GetExamList: 获取讨论记录
-// todo
-func (wk *WK) GetDiscussList(courseID, page string) (*AllRecordResp[ExamList], error) {
-	return GetRecords[ExamList](wk, RecordStudy, courseID, page)
+// GetDiscussList: 获取讨论记录
+func (wk *WK) GetDiscussList(courseID, page string) (*AllRecordResp[StudyList], error) {
+	return GetRecords[StudyList](wk, RecordDiscuss, courseID, page)
 }
 
 func isLoginTimeoutBody(body []byte) bool {