Measurement: save 'Show Delta' state between commands #19204 (#19430)

* Measurement: save 'Show Delta' state between commands #19204

When users set Show Delta option to off in the Measure tool, the setting
was not being preserved when the tool was invoked again. This was due to    
using an uninitialized value as the default when loading the preference.  

Changes staged in: FreeCAD\src\Mod\Measure\Gui\TaskMeasure.cpp 

Fixed by:
- Using explicit 'true' as default value when loading Show Delta
preference 
- Maintains existing save functionality
- Ensures consistent behavior on first use
Fixes #19204

* Changed few things to ensure the delta state is saved #19204

added changes:-
1. settings.endGroup()
When we call beginGroup(), it creates a prefix for all subsequent settings operations, All settings will be stored under the "TaskMeasure" group.
endGroup() is needed to close this grouping scope
Without it, subsequent settings operations would still use the "TaskMeasure" prefix

2. settings.sync()
By default, QSettings caches changes in memory and writes them to disk later
sync() makes an immediate write to the settings file
This ensures the setting is saved right away rather than waiting for Qt to decide when to save.
Makes the setting change immediately available for future commands.

-Fixes Measurement: save 'Show Delta' state between commands #19204

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Added proposed changes to autoSaveChanged() and newMeasurementBehaviourChanged() functions #19204 #19430

Added settings.endGroup() to the following functions:-
1.autoSaveChanged()
2.newMeasurementBehaviourChanged() 
Each beginGroup() should be followed by endGroup().

No need for explicitily calling sync() as it is called automatically from QSettings's destructor and by the event loop at regular intervals.(Refer documentation for more info)

-Fixes Measurement: save 'Show Delta' state between commands #19204 #19430

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/Mod/Measure/Gui/TaskMeasure.cpp

@@ -72,7 +72,7 @@ TaskMeasure::TaskMeasure()
 
     QSettings settings;
     settings.beginGroup(QLatin1String(taskMeasureSettingsGroup));
-    delta = settings.value(QLatin1String(taskMeasureShowDeltaSettingsName), delta).toBool();
+    delta = settings.value(QLatin1String(taskMeasureShowDeltaSettingsName), true).toBool();
     mAutoSave = settings.value(QLatin1String(taskMeasureAutoSaveSettingsName), mAutoSave).toBool();
     if (settings.value(QLatin1String(taskMeasureGreedySelection), false).toBool()) {
         Gui::Selection().setSelectionStyle(SelectionStyle::GreedySelection);
@@ -80,6 +80,7 @@ TaskMeasure::TaskMeasure()
     else {
         Gui::Selection().setSelectionStyle(SelectionStyle::NormalSelection);
     }
+    settings.endGroup();
 
     showDelta = new QCheckBox();
     showDelta->setChecked(delta);
@@ -526,6 +527,8 @@ void TaskMeasure::showDeltaChanged(int checkState)
     QSettings settings;
     settings.beginGroup(QLatin1String(taskMeasureSettingsGroup));
     settings.setValue(QLatin1String(taskMeasureShowDeltaSettingsName), delta);
+    settings.endGroup();
+    settings.sync();  // immediate write to the settings file
 
     this->update();
 }
@@ -537,6 +540,7 @@ void TaskMeasure::autoSaveChanged(bool checked)
     QSettings settings;
     settings.beginGroup(QLatin1String(taskMeasureSettingsGroup));
     settings.setValue(QLatin1String(taskMeasureAutoSaveSettingsName), mAutoSave);
+    settings.endGroup();
 }
 
 void TaskMeasure::newMeasurementBehaviourChanged(bool checked)
@@ -551,6 +555,7 @@ void TaskMeasure::newMeasurementBehaviourChanged(bool checked)
         Gui::Selection().setSelectionStyle(SelectionStyle::GreedySelection);
         settings.setValue(QLatin1String(taskMeasureGreedySelection), true);
     }
+    settings.endGroup();
 }
 
 void TaskMeasure::setModeSilent(App::MeasureType* mode)