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.

src/gui_2.py

@@ -1185,15 +1185,12 @@ class App:
   
   # Draw right-aligned window controls directly in the menu bar (Win32 only)
   if sys.platform == "win32":
-   try:
-    import ctypes
-    ctypes.pythonapi.PyCapsule_GetPointer.restype  = ctypes.c_void_p
-    ctypes.pythonapi.PyCapsule_GetPointer.argtypes = [ctypes.py_object, ctypes.c_char_p]
-    hwnd_capsule = imgui.get_main_viewport().platform_handle_raw
-    hwnd         = ctypes.pythonapi.PyCapsule_GetPointer(hwnd_capsule, b"nb_handle")
-   except Exception:
-    hwnd = 0
-   
+   result = _show_menus_hwnd_result(self)
+   if not result.ok:
+    if not hasattr(self, '_last_request_errors'): self._last_request_errors = []
+    self._last_request_errors.append(("_show_menus.hwnd", result.errors[0]))
+   hwnd = result.data
+
    if hwnd:
     btn_w = 40
     # Use window width (points) instead of display_size (pixels) for correct scaling
@@ -7528,6 +7525,35 @@ def _show_menus_do_generate_result(app: "App") -> Result[bool]:
    original=e,
   )])
 
+def _show_menus_hwnd_result(app: "App") -> Result[int]:
+ """Drain-aware variant of L1197 _show_menus hwnd capsule try/except.
+
+ Extracts the ctypes PyCapsule_GetPointer try/except from App._show_menus
+ into a Result-returning helper. On success, returns Result(data=hwnd)
+ where hwnd is the resolved window handle. On failure (e.g., on a
+ non-Windows platform), returns Result(data=0, errors=[ErrorInfo]).
+
+ The data field is the resolved hwnd (int) so the legacy wrapper can
+ pass it to subsequent win32gui calls without an additional app.hwnd
+ instance attribute.
+
+ [C: src/gui_2.py:App._show_menus (L1197 legacy wrapper)]
+ """
+ try:
+  import ctypes
+  ctypes.pythonapi.PyCapsule_GetPointer.restype  = ctypes.c_void_p
+  ctypes.pythonapi.PyCapsule_GetPointer.argtypes = [ctypes.py_object, ctypes.c_char_p]
+  hwnd_capsule = imgui.get_main_viewport().platform_handle_raw
+  hwnd         = ctypes.pythonapi.PyCapsule_GetPointer(hwnd_capsule, b"nb_handle")
+  return Result(data=int(hwnd) if hwnd else 0)
+ except Exception as e:
+  return Result(data=0, errors=[ErrorInfo(
+   kind=ErrorKind.INTERNAL,
+   message=f"Failed to resolve hwnd via PyCapsule_GetPointer: {e}",
+   source="gui_2._show_menus_hwnd_result",
+   original=e,
+  )])
+
 #endregion: Phase 3 Render-Loop Result Helpers
 
 #endregion: MMA