fix(agent): filter TuShare news with upstream keyword input (#16361)

## Summary

TuShare required non-empty upstream input but filtered fetched news with
the static `keyword` param (default empty string), so agent-provided
keywords were ignored.

Use `self._param.keyword or ans` when filtering, matching how AkShare
uses upstream input for its query.

Fixes #16360

## Test plan

- [x] `test_tushare_filters_with_upstream_keyword_when_param_empty`
mocks the API and asserts only rows matching the upstream keyword are
returned

---------

Co-authored-by: yzc <yuzhichang@gmail.com>
Co-authored-by: Harsh Kashyap <harshkashyap@Harshs-MacBook-Pro.local>

agent/tools/tushare.py

@@ -14,6 +14,7 @@
 #  limitations under the License.
 #
 import json
+import logging
 from abc import ABC
 import pandas as pd
 import time
@@ -73,7 +74,18 @@ class TuShare(ComponentBase, ABC):
             df.columns = response['data']['fields']
             if self.check_if_canceled("TuShare processing"):
                 return
-            tus_res.append({"content": (df[df['content'].str.contains(self._param.keyword, case=False)]).to_markdown()})
+            keyword = self._param.keyword or ans
+            logging.info(
+                "TuShare news filter keyword source=%s",
+                "param.keyword" if self._param.keyword else "upstream_input",
+            )
+            tus_res.append(
+                {
+                    "content": (
+                        df[df["content"].str.contains(keyword, case=False, na=False, regex=False)]
+                    ).to_markdown()
+                }
+            )
         except Exception as e:
             if self.check_if_canceled("TuShare processing"):
                 return