fix: Polymarket SSH代理增强错误处理

- 捕获subprocess超时
- 检查空响应
- 捕获JSON解析错误
- 更清晰的错误信息

tradingagents/dataflows/polymarket.py

@@ -52,10 +52,18 @@ def _request(path: str, params: dict) -> dict:
             "-p", str(port), f"root@{host}",
             f'curl -s "{full_url}"'
         ]
-        result = subprocess.run(cmd, capture_output=True, text=True, timeout=REQUEST_TIMEOUT)
+        try:
+            result = subprocess.run(cmd, capture_output=True, text=True, timeout=REQUEST_TIMEOUT)
+        except subprocess.TimeoutExpired:
+            raise requests.RequestException("SSH proxy timed out")
         if result.returncode != 0:
             raise requests.RequestException(f"SSH proxy failed: {result.stderr}")
-        return json.loads(result.stdout)
+        if not result.stdout or not result.stdout.strip():
+            raise requests.RequestException("SSH proxy returned empty response")
+        try:
+            return json.loads(result.stdout)
+        except json.JSONDecodeError as e:
+            raise requests.RequestException(f"SSH proxy returned invalid JSON: {e}")
 
 
 def _parse_json_list(value) -> list: