refactor(gui_2): migrate L1197 _show_menus hwnd to Result[T] (Phase 3)

TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 3.

Adds _show_menus_hwnd_result(app) -> Result[int] helper that wraps the
ctypes PyCapsule_GetPointer try/except from App._show_menus. The data
field carries the resolved hwnd (or 0 on failure) so the legacy wrapper
can pass it to subsequent win32gui calls without an additional app.hwnd
instance attribute.

App._show_menus becomes a thin wrapper that drains errors to
_last_request_errors when the hwnd capsule resolution fails.

Audit: BROAD_CATCH count 21 -> 20, COMPLIANT count 16 -> 17. Tests: 2/2 pass.

tests/test_gui_2_result.py

@@ -378,4 +378,45 @@ def test_phase_3_l1171_show_menus_do_generate_result_failure():
  err = result.errors[0]
  assert err.source == "gui_2._show_menus_do_generate_result"
  assert "generate blew up" in err.message
- assert "error" in app.ai_status
+ assert "error" in app.ai_status
+
+
+def test_phase_3_l1197_show_menus_hwnd_result_success():
+ """
+ L1197 _show_menus_hwnd_result returns Result.ok=True on success.
+
+ The helper wraps the ctypes PyCapsule_GetPointer try/except in
+ App._show_menus. On success, returns Result(data=hwnd) with the
+ resolved window handle.
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ mock_viewport = MagicMock()
+ mock_viewport.platform_handle_raw = "mock_capsule"
+ with patch.object(gui_2.imgui, "get_main_viewport", return_value=mock_viewport), \
+   patch("ctypes.pythonapi.PyCapsule_GetPointer", return_value=12345):
+  result = gui_2._show_menus_hwnd_result(app)
+ assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
+ assert result.data == 12345
+
+
+def test_phase_3_l1197_show_menus_hwnd_result_failure():
+ """
+ L1197 _show_menus_hwnd_result returns Result.ok=False with ErrorInfo on failure.
+
+ When the ctypes call raises (e.g., on a non-Windows platform or when
+ imgui.get_main_viewport returns None), the helper returns
+ Result(data=0, errors=[ErrorInfo]).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ # Force the except branch by raising inside the try block
+ with patch.object(gui_2.imgui, "get_main_viewport", side_effect=RuntimeError("no viewport")):
+  result = gui_2._show_menus_hwnd_result(app)
+ assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
+ assert result.errors, "Expected at least one error on failure"
+ err = result.errors[0]
+ assert err.source == "gui_2._show_menus_hwnd_result"
+ assert result.data == 0