feat(agent): 支持自定义系统提示词进行对话

- 前端 API 新增 customSystemPrompt 参数，agentId 变为可选
- 聊天抽屉支持自定义提示词时传递参数并调整宽度
- 我的收藏模态框返回提示词内容供聊天使用
- 后端 Dify 服务优先使用自定义提示词，支持无 agentId 的对话
- Dify 请求 VO 中 agentId 改为非必填，新增 customSystemPrompt 字段

yudao-module-tik/src/main/java/cn/iocoder/yudao/module/tik/dify/service/DifyServiceImpl.java

@@ -50,13 +50,24 @@ public class DifyServiceImpl implements DifyService {
         AtomicLong pendingRecordId = new AtomicLong();
         AtomicReference<String> conversationIdRef = new AtomicReference<>(reqVO.getConversationId());
         AtomicReference<DifyChatRespVO> tokenUsageRef = new AtomicReference<>();
-        String difyUserId = "user-" + userId + "-agent-" + reqVO.getAgentId();
+        String difyUserId = reqVO.getAgentId() != null
+                ? "user-" + userId + "-agent-" + reqVO.getAgentId()
+                : "user-" + userId + "-prompt";
         String logPrefix = "chatStream";
 
         return Mono.fromCallable(() -> {
-                    AiAgentDO agent = aiAgentService.getAiAgent(reqVO.getAgentId());
-                    if (agent == null) {
-                        throw new RuntimeException("智能体不存在");
+                    // 解析系统提示词：优先使用自定义提示词，否则从智能体获取
+                    String systemPrompt;
+                    if (reqVO.getCustomSystemPrompt() != null && !reqVO.getCustomSystemPrompt().isEmpty()) {
+                        systemPrompt = reqVO.getCustomSystemPrompt();
+                    } else if (reqVO.getAgentId() != null) {
+                        AiAgentDO agent = aiAgentService.getAiAgent(reqVO.getAgentId());
+                        if (agent == null) {
+                            throw new RuntimeException("智能体不存在");
+                        }
+                        systemPrompt = agent.getSystemPrompt();
+                    } else {
+                        throw new RuntimeException("必须提供 agentId 或 customSystemPrompt");
                     }
 
                     AiModelTypeEnum modelTypeEnum = "standard".equals(reqVO.getModelMode())
@@ -66,12 +77,15 @@ public class DifyServiceImpl implements DifyService {
                             AiPlatformEnum.DIFY.getPlatform(), modelTypeEnum.getModelCode());
 
                     pointsService.checkPoints(userId, config.getConsumePoints());
+                    String serviceRef = reqVO.getAgentId() != null
+                            ? reqVO.getAgentId().toString()
+                            : "custom-prompt";
                     Long recordId = pointsService.createPendingDeduct(
                             userId, config.getConsumePoints(), "dify_chat",
-                            reqVO.getAgentId().toString(), config.getServiceCode());
+                            serviceRef, config.getServiceCode());
                     pendingRecordId.set(recordId);
 
-                    return new DifyChatContext(agent.getSystemPrompt(), config.getApiKey(), config.getConsumePoints());
+                    return new DifyChatContext(systemPrompt, config.getApiKey(), config.getConsumePoints());
                 })
                 .flatMapMany(context -> difyClient.chatStream(
                                 context.apiKey(), reqVO.getContent(), context.systemPrompt(),

yudao-module-tik/src/main/java/cn/iocoder/yudao/module/tik/dify/vo/DifyChatReqVO.java

@@ -12,8 +12,7 @@ import lombok.Data;
 @Data
 public class DifyChatReqVO {
 
-    @Schema(description = "智能体ID", requiredMode = Schema.RequiredMode.REQUIRED)
-    @NotNull(message = "智能体ID不能为空")
+    @Schema(description = "智能体ID（使用 customSystemPrompt 时可不传）")
     private Long agentId;
 
     @Schema(description = "用户输入内容", requiredMode = Schema.RequiredMode.REQUIRED)
@@ -26,4 +25,7 @@ public class DifyChatReqVO {
     @Schema(description = "模型模式：pro-深度版 standard-标准版", example = "pro")
     private String modelMode = "pro";
 
+    @Schema(description = "自定义系统提示词（使用用户自建风格时传入）")
+    private String customSystemPrompt;
+
 }