fix: use append instead of fragile insert chain in PartDesign menu (#57)

Replace the chained insert operations in modifyMenuBar() with independent
append operations. The old approach anchored on PartDesign_Boolean and
chained each subsequent command off the previous insertion — a single
missing anchor caused a cascade failure.

The new approach uses append with PartDesign_Body as the parent locator.
Each operation is independent, so a failure in one does not affect the
others.

ztools/InitGui.py

@@ -365,26 +365,10 @@ class _ZToolsPartDesignManipulator:
 
     def modifyMenuBar(self):
         return [
-            {
-                "insert": "ZTools_DatumCreator",
-                "menuItem": "PartDesign_Boolean",
-                "after": "",
-            },
-            {
-                "insert": "ZTools_DatumManager",
-                "menuItem": "ZTools_DatumCreator",
-                "after": "",
-            },
-            {
-                "insert": "ZTools_EnhancedPocket",
-                "menuItem": "ZTools_DatumManager",
-                "after": "",
-            },
-            {
-                "insert": "ZTools_RotatedLinearPattern",
-                "menuItem": "ZTools_EnhancedPocket",
-                "after": "",
-            },
+            {"append": "ZTools_DatumCreator", "menuItem": "PartDesign_Body"},
+            {"append": "ZTools_DatumManager", "menuItem": "PartDesign_Body"},
+            {"append": "ZTools_EnhancedPocket", "menuItem": "PartDesign_Body"},
+            {"append": "ZTools_RotatedLinearPattern", "menuItem": "PartDesign_Body"},
         ]