fix: 使用终态答案校正流式输出

- DONE 事件携带后端汇总的完整最终正文

- 前端完成时替换可能受损的流式文本

- 补充文件 URL 终态校正回归测试

easyflow-modules/easyflow-module-agent/src/main/java/tech/easyflow/agent/runtime/AgentRunService.java

@@ -930,7 +930,7 @@ public class AgentRunService {
                     buildAssistantRuntimeMessage(chatContext, finalAnswer, assistantAccumulator, citations));
             chatRuntimeManager.recordCompleted(chatContext);
         }
-        sendDone(chatSseEmitter);
+        sendDone(chatSseEmitter, finalAnswer);
     }
 
     private void handleRuntimeError(Throwable error,
@@ -1184,10 +1184,30 @@ public class AgentRunService {
         return chatSseEmitter.send(envelope);
     }
 
+    /**
+     * 发送不携带最终正文的完成事件。
+     *
+     * @param chatSseEmitter SSE 发送器
+     * @return 发送成功时为 {@code true}
+     */
     private boolean sendDone(ChatSseEmitter chatSseEmitter) {
+        return sendDone(chatSseEmitter, null);
+    }
+
+    /**
+     * 发送完成事件，并提供最终正文供前端校正流式增量。
+     *
+     * @param chatSseEmitter SSE 发送器
+     * @param finalText 最终完整正文；取消场景可为空
+     * @return 发送成功时为 {@code true}
+     */
+    private boolean sendDone(ChatSseEmitter chatSseEmitter, String finalText) {
         ChatEnvelope<Map<String, Object>> envelope = new ChatEnvelope<>();
         envelope.setDomain(ChatDomain.SYSTEM);
         envelope.setType(ChatType.DONE);
+        if (finalText != null) {
+            envelope.setPayload(Map.of("finalText", finalText));
+        }
         return chatSseEmitter.sendDone(envelope);
     }
 

easyflow-modules/easyflow-module-agent/src/test/java/tech/easyflow/agent/runtime/AgentRunServiceDraftAndHitlTest.java

@@ -229,8 +229,14 @@ public class AgentRunServiceDraftAndHitlTest {
         Assert.assertEquals("先分析", reasoning.toString());
         Assert.assertEquals("\n最终回答", content.toString());
         Assert.assertEquals("\n最终回答", answer.toString());
-        Assert.assertTrue(emitter.envelopes.stream().anyMatch(envelope ->
-                envelope.getDomain() == ChatDomain.SYSTEM && envelope.getType() == ChatType.DONE));
+        ChatEnvelope<?> done = emitter.envelopes.stream()
+                .filter(envelope -> envelope.getDomain() == ChatDomain.SYSTEM
+                        && envelope.getType() == ChatType.DONE)
+                .findFirst()
+                .orElseThrow();
+        @SuppressWarnings("unchecked")
+        Map<String, Object> donePayload = (Map<String, Object>) done.getPayload();
+        Assert.assertEquals("\n最终回答", donePayload.get("finalText"));
     }
 
     /**