fix(agent/tools): port AkShare to ToolBase so it works as an Agent tool (#16417)

### What problem does this PR solve?

Closes #16416.

The **AkShare** agent tool (`agent/tools/akshare.py`) was never ported
to the modern `ToolBase`/`_invoke` interface during the agent module
redesign and was still written against the removed legacy
`_run`/`be_output` API, so it was non-functional:

1. **Adding it to an Agent raised `AttributeError`.** `AkShare` extended
`ComponentBase` (not `ToolBase`) and `AkShareParam` defined no `meta`,
so it had no `get_meta()`. `agent/component/agent_with_tools.py` builds
each tool's function descriptor via `cpn.get_meta()`, so constructing an
Agent that includes the AkShare tool raised `AttributeError: 'AkShare'
object has no attribute 'get_meta'`.
2. **It could never run.** `invoke()` dispatches to `self._invoke`, but
`AkShare` only implemented the legacy `_run`, so `_invoke` fell through
to `ComponentBase._invoke` → `NotImplementedError`. `_run` also called
`be_output(...)`, which no longer exists on the base classes.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

### Changes

- Port `AkShareParam` to `ToolParamBase` with a `ToolMeta` (defined
before `super().__init__()`, matching `ArXivParam`/`TavilyExtractParam`)
exposing a required `query` parameter — the stock symbol to look up,
default `{sys.query}`. `query` matches the `{sys.query}` convention
shared by the other tools.
- Rewrite the component with `_invoke`/`set_output("formalized_content",
...)` (errors surfaced via `_ERROR`), keeping `top_n` and importing
`akshare` lazily.
- Add regression tests
(`test/unit_test/agent/component/test_akshare.py`) covering param
construction, validation, and the tool descriptor.

Same class of defect as #16329 (DeepL) and #16414 (Crawler).
Backend-only; no frontend changes.

---------

Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

test/unit_test/agent/component/test_akshare.py

@@ -0,0 +1,99 @@
+#
+#  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+import pytest
+
+from agent.tools.akshare import AkShare, AkShareParam
+
+
+def _make_tool(top_n=10):
+    # Bypass the canvas-bound __init__ (mirrors test_pubmed_unit.py) and stub the
+    # canvas-touching helpers so we can exercise _invoke's execution path.
+    tool = AkShare.__new__(AkShare)
+    param = AkShareParam()
+    param.top_n = top_n
+    tool._param = param
+    tool.check_if_canceled = lambda *a, **k: False
+    out = {}
+    tool.set_output = lambda k, v: out.__setitem__(k, v)
+    tool.output = lambda k=None: (out.get(k) if k else out)
+    return tool, out
+
+
+def _fake_news_df(n):
+    import pandas as pd
+
+    return pd.DataFrame(
+        [
+            {
+                "新闻链接": f"https://u{i}",
+                "新闻标题": f"title{i}",
+                "新闻内容": f"content{i}",
+                "发布时间": "2026-01-01",
+                "文章来源": "src",
+            }
+            for i in range(n)
+        ]
+    )
+
+
+def test_param_instantiates():
+    AkShareParam()
+
+
+def test_check_passes_with_defaults():
+    AkShareParam().check()
+
+
+def test_meta_exposes_query_parameter():
+    # Regression: AkShare extended ComponentBase and defined no `meta`, so it
+    # had no get_meta() and crashed agent_with_tools when added to an Agent.
+    meta = AkShareParam().get_meta()
+    params = meta["function"]["parameters"]
+    assert "query" in params["properties"]
+    assert "query" in params["required"]
+
+
+def test_check_rejects_non_positive_top_n():
+    param = AkShareParam()
+    param.top_n = 0
+    with pytest.raises(ValueError):
+        param.check()
+
+
+def test_invoke_returns_content_and_sets_formalized_content(monkeypatch):
+    # Regression for the restored runtime path: _invoke(query=...) must fetch
+    # news, return the formatted content, write it to formalized_content, and
+    # respect top_n.
+    pytest.importorskip("akshare")
+    import akshare
+
+    monkeypatch.setattr(akshare, "stock_news_em", lambda symbol: _fake_news_df(5))
+
+    tool, out = _make_tool(top_n=2)
+    res = tool._invoke(query="600519")
+
+    assert "title0" in res and "https://u0" in res
+    assert out["formalized_content"] == res
+    # top_n is applied via .head(top_n): only 2 articles formatted.
+    assert res.count("新闻内容:") == 2
+
+
+def test_invoke_empty_query_returns_empty():
+    # Empty query short-circuits without calling akshare.
+    tool, out = _make_tool()
+    assert tool._invoke(query="") == ""
+    assert out.get("formalized_content") == ""