Python: Add second approval-required tool (set_stop_loss) to concurrent_builder_tool_approval sample (#4875)

* Add set_stop_loss tool to concurrent_builder_tool_approval sample

Add a second approval-gated tool (set_stop_loss) to the concurrent workflow
tool approval sample to demonstrate handling approval requests for different
tools in the same concurrent workflow.

Changes:
- Add set_stop_loss(symbol, stop_price) with approval_mode='always_require'
- Include new tool in both agents' tool lists
- Update agent instructions and prompt to encourage stop-loss usage
- Update docstring to reflect two approval-gated tools
- Update sample output to show mixed approval requests

Fixes #4874

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Print tool name and arguments in concurrent sample's process_event_stream (#4874)

Align process_event_stream in concurrent_builder_tool_approval.py to print
the tool name and arguments when collecting approval requests, matching the
sample output comment and the sequential_builder_tool_approval.py pattern.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add None-guard for function_call access in tool approval sample (#4874)

Add explicit None-checks before accessing function_call.name and
function_call.arguments in concurrent_builder_tool_approval.py. The
function_call field is typed Content | None, so direct attribute access
without a guard could raise AttributeError and required type: ignore
comments. The None-guard is consistent with the pattern used in
_agent_run.py and removes the suppression comments.

Also add a regression test verifying that function_call defaults to None
and that the None-guard pattern is safe.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Apply same function_call None-guard to sibling tool-approval samples (#4874)

Apply the same fix to sequential_builder_tool_approval.py and
group_chat_builder_tool_approval.py, which had the identical pattern
of accessing function_call.name/arguments without a None-guard.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <copilot@github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/core/tests/core/test_types.py

@@ -664,6 +664,21 @@ def test_function_approval_serialization_roundtrip():
     # The Content union will need to be handled differently when we fully migrate
 
 
+def test_function_approval_request_function_call_none_guard():
+    """Test that accessing function_call attributes is safe when function_call is None."""
+    # Construct a Content with type "function_approval_request" but no function_call.
+    # This verifies the None-guard pattern used in samples to prevent AttributeError.
+    content = Content("function_approval_request", id="req-none")
+    assert content.function_call is None
+
+    # A proper approval request always has function_call set
+    fc = Content.from_function_call(call_id="call-1", name="do_something", arguments={"a": 1})
+    req = Content.from_function_approval_request(id="req-1", function_call=fc)
+    assert req.function_call is not None
+    assert req.function_call.name == "do_something"
+    assert req.function_call.arguments == {"a": 1}
+
+
 def test_function_approval_accepts_mcp_call():
     """Ensure FunctionApprovalRequestContent supports MCP server tool calls."""
     mcp_call = Content.from_mcp_server_tool_call(