fix(chat_dashboard): improve JSON parsing robustness in output parser

Adds error handling and recovery mechanisms for malformed JSON responses
  from LLM models in the chat dashboard scene.

  Changes:
  - Add try-catch blocks with progressive fallback strategies for JSON parsing
  - Implement _clean_json_string() method to handle common JSON formatting issues
  - Add _extract_json_fallback() method for regex-based JSON extraction
  - Add proper logging for JSON parsing failures and recovery attempts

packages/dbgpt-app/src/dbgpt_app/scene/chat_dashboard/out_parser.py

@@ -23,7 +23,20 @@ class ChatDashboardOutputParser(BaseOutputParser):
     def parse_prompt_response(self, model_out_text):
         clean_str = super().parse_prompt_response(model_out_text)
         print("clean prompt response:", clean_str)
-        response = json.loads(clean_str)
+
+        try:
+            response = json.loads(clean_str)
+        except json.JSONDecodeError as e:
+            logger.warning(f"JSON parsing failed: {e}. Attempting to clean and retry.")
+            cleaned_str = self._clean_json_string(clean_str)
+            try:
+                response = json.loads(cleaned_str)
+            except json.JSONDecodeError:
+                logger.warning("JSON cleaning failed. Attempting fallback extraction.")
+                response = self._extract_json_fallback(clean_str)
+                if response is None:
+                    raise ValueError(f"Unable to parse JSON from response: {clean_str}")
+
         chart_items: List[ChartItem] = []
         if not isinstance(response, list):
             response = [response]
@@ -38,6 +51,43 @@ class ChatDashboardOutputParser(BaseOutputParser):
             )
         return chart_items
 
+    def _clean_json_string(self, json_str: str) -> str:
+        """Clean common JSON formatting issues."""
+        # Remove leading/trailing whitespace
+        json_str = json_str.strip()
+
+        # Remove markdown code blocks if present
+        if json_str.startswith("```"):
+            lines = json_str.split("\n")
+            if len(lines) > 1:
+                # Remove first line (```json or ```)
+                json_str = "\n".join(lines[1:])
+                # Remove last line if it's just ```
+                if json_str.strip().endswith("```"):
+                    json_str = json_str.strip()[:-3]
+
+        # Fix common escaping issues
+        json_str = json_str.replace('\\"', '"')
+        json_str = json_str.replace("\\\\", "\\")
+
+        return json_str.strip()
+
+    def _extract_json_fallback(self, text: str) -> dict:
+        """Extract JSON using regex as fallback."""
+        import re
+
+        # Look for JSON-like structures
+        json_pattern = r"\{[^{}]*(?:\{[^{}]*\}[^{}]*)*\}"
+        matches = re.findall(json_pattern, text, re.DOTALL)
+
+        for match in matches:
+            try:
+                return json.loads(match)
+            except json.JSONDecodeError:
+                continue
+
+        return None
+
     def parse_view_response(self, speak, data, prompt_response) -> str:
         return json.dumps(data.prepare_dict(), ensure_ascii=False)