extract MainWindow::reloadConfig

The three restart paths each repeated the same config + visuals reload with
its own try/catch and error dialog. Only that shared part is extracted; each
site keeps its own follow-up (ResetCommand vs. direct Simulation::reset) and
its own error-path cleanup.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GH8ZMRY3vhxxXcaUxBqxkk

src/ui/MainWindow.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
@@ -9,6 +10,7 @@
 #include "BuildingId.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventHandler.h"
+#include "GameConfig.h"
 #include "GameOverEvent.h"
 #include "LayoutDialogRequestedEvent.h"
 #include "ModalDimOverlay.h"
@@ -58,6 +60,12 @@ private:
     void handleEvent(std::shared_ptr<const LayoutDialogRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const RecipeSelectionRequestedEvent> event) override;
 
+    // Reloads the game config and visuals.toml from disk (REQ-CFG-RELOAD), shared
+    // by every restart path. On success the reloaded visuals are applied to this
+    // window and the fresh GameConfig is returned; on failure a modal error dialog
+    // is shown and std::nullopt is returned, leaving the window state untouched.
+    std::optional<GameConfig> reloadConfig();
+
     // Opens the shipyard layout configuration dialog for the given schematic and
     // current layout, applying the result via SetShipLayoutCommand (REQ-MOD-UI-DIALOG).
     void openShipLayoutDialog(BuildingId shipyardId,