Fix B-spline keyboard focus issue (#23859) (#23860)

* Fix B-spline keyboard focus issue (#23859)

- Restore keyboard focus after command restart in changeConstructionMethode()
- Fixes M key mode switching and R toggle periodic functionality
- Uses direct MDI view focus restoration instead of private ensureFocus() method

Fixes issue where keyboard shortcuts stop working after first mode switch.

* Address Copilot feedback: Add null check for activeDocument()

- Use ternary operator for cleaner null safety
- Prevents potential crash if activeDocument() returns null
- More idiomatic C++ code style

* Improve variable scope per @chennes feedback

- Use if-with-initialization to scope doc and mdi variables
- Variables now only exist where needed instead of leaking into function scope
- More idiomatic C++ code style

src/Mod/Sketcher/Gui/DrawSketchHandlerBSpline.h

@@ -747,6 +747,13 @@ private:
         tryAutoRecomputeIfNotSolve(sketchgui->getSketchObject());
         Gui::Command::openCommand(QT_TRANSLATE_NOOP("Command", "Add Sketch B-Spline"));
 
+        // Restore keyboard focus after command restart
+        if (Gui::Document* doc = Gui::Application::Instance->activeDocument()) {
+            if (Gui::MDIView* mdi = doc->getActiveView()) {
+                mdi->setFocus();
+            }
+        }
+
         // Add the necessary alignment geometries and constraints
         for (size_t i = 0; i < geoIds.size(); ++i) {
             addGeometry(points[i], geoIds[i], i == 0);