TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 10: refactor(gui_2): migrate L1052 shutdown save_ini to Result[T] (Phase 10 site 5)

Extracted _shutdown_save_ini_result(app) -> Result[None] helper above
the App.shutdown method.
ANTI-SLIMING: full Result[T] propagation (NO bare-except+pass). The
helper returns Result(data=None) on success or Result(data=None,
errors=[ErrorInfo]) on exception (logging NOT a drain per the user's
principle 2026-06-17).

The legacy shutdown method preserves its signature, calls the helper,
drains errors to self._startup_timeline_errors, and proceeds to
self.controller.shutdown().

Tests: 2 new tests verify both paths (success and OSError).

Audit: L1052 reclassified from INTERNAL_SILENT_SWALLOW (9 sites remaining,
was 10). New helper L1052 is INTERNAL_COMPLIANT.

src/gui_2.py

@@ -1045,14 +1045,35 @@ def _run_immapp_result(app: "App") -> Result[None]:
   forces a save of dirty registries/caches, and terminates the active thread pools.
   SSDL Shape: `[I:save_ini] -> [I:controller_shutdown]`
   """
-  #Note(Ed): Exception(Thirdparty)
-  try:
-   if hasattr(self, 'runner_params') and self.runner_params.ini_filename:
-    imgui.save_ini_settings_to_disk(self.runner_params.ini_filename)
-  except:
-   pass
+  ini_result = _shutdown_save_ini_result(self)
+  if not ini_result.ok:
+   if not hasattr(self, '_startup_timeline_errors'): self._startup_timeline_errors = []
+   self._startup_timeline_errors.append(("shutdown.save_ini", ini_result.errors[0]))
   self.controller.shutdown()
 
+def _shutdown_save_ini_result(app: "App") -> Result[None]:
+ """Drain-aware variant of App.shutdown save_ini try block (L1052 INTERNAL_SILENT_SWALLOW).
+
+ Extracts the thirdparty imgui.save_ini_settings_to_disk try/except from
+ App.shutdown into a Result-returning helper. On exception, converts to
+ ErrorInfo (logging NOT a drain per the user's principle 2026-06-17). The
+ legacy shutdown method drains to self._startup_timeline_errors.
+
+ [C: src/gui_2.py:App.shutdown (L1052 legacy wrapper)]
+ """
+ #Note(Ed): Exception(Thirdparty)
+ try:
+  if hasattr(app, 'runner_params') and app.runner_params.ini_filename:
+   imgui.save_ini_settings_to_disk(app.runner_params.ini_filename)
+  return Result(data=None)
+ except Exception as e:
+  return Result(data=None, errors=[ErrorInfo(
+   kind=ErrorKind.INTERNAL,
+   message=f"imgui.save_ini_settings_to_disk failed: {e}",
+   source="gui_2._shutdown_save_ini_result",
+   original=e,
+  )])
+
  def load_context_preset(self, name: str) -> None:
   preset = self.controller.load_context_preset(name)
   from src import models