fix: handle JSONDecodeError in search, simplify local_search serialization

- Add json.JSONDecodeError to _do_search exception handling so malformed
  registry responses return an error dict instead of crashing
- Replace model_dump_json + json.loads with model_dump in _local_search
  to avoid unnecessary serialize-then-deserialize roundtrip
- Remove unnecessary `as _` in test patch context managers
- Fix 80-char line limit violation in test docstring

Author: zeroasterisk

src/google/adk_community/tools/ardhf/ardhf_toolset.py

@@ -161,10 +161,8 @@ def _local_search(
       pageSize=limit,
   )
   response = search_agent_finder(request, token=token)
-  return json.loads(
-      response.model_dump_json(
-          exclude_none=True, exclude_defaults=True
-      )
+  return response.model_dump(
+      exclude_none=True, exclude_defaults=True
   )
 
 
@@ -285,7 +283,7 @@ async def _do_search(
           limit=limit,
           token=self._token,
       )
-    except (HTTPError, URLError, TimeoutError) as exc:
+    except (HTTPError, URLError, TimeoutError, json.JSONDecodeError) as exc:
       logger.warning("ARD search failed: %s", exc)
       return {"error": f"Search request failed: {exc}"}
     except ImportError as exc:

tests/unittests/tools/ardhf/test_ardhf_toolset.py

@@ -110,7 +110,7 @@ class TestToolsetGetTools:
 
   @pytest.mark.asyncio
   async def test_returns_all_tools(self):
-    """The toolset exposes all search aliases plus get_agent_card and connect_agent."""
+    """All seven tools are exposed by default."""
     toolset = AgentFinderToolset()
 
     tools = await toolset.get_tools()
@@ -504,11 +504,11 @@ async def mock_send_message(**kwargs):
         patch(
             "a2a.client.card_resolver.A2ACardResolver",
             return_value=mock_resolver,
-        ) as _,
+        ),
         patch(
             "a2a.client.client_factory.ClientFactory",
             return_value=mock_factory,
-        ) as _,
+        ),
     ):
       result = await connect_tool.run_async(
           args={