fix: address review issues in NSUndoManager migration

- Fix primaryKeyChange undo closure capturing stale workingPrimaryKey
- Fix batch insertion undo leaking insertedRowData entries
- Clear undo history in loadSchema to prevent stale actions on table switch
- Make undoManager private to prevent bypass of lastUndoResult contract

Author: datlechin

TablePro/Core/ChangeTracking/DataChangeManager.swift

@@ -98,7 +98,7 @@ final class DataChangeManager {
         return lo
     }
 
-    let undoManager: UndoManager = {
+    private let undoManager: UndoManager = {
         let manager = UndoManager()
         manager.levelsOfUndo = 100
         manager.groupsByEvent = false
@@ -606,6 +606,7 @@ final class DataChangeManager {
                 for rowIndex in rowIndices {
                     removeChangeByKey(rowIndex: rowIndex, type: .insert)
                     insertedRowIndices.remove(rowIndex)
+                    insertedRowData.removeValue(forKey: rowIndex)
                     changedRowIndices.insert(rowIndex)
                 }
                 lastUndoResult = UndoResult(

TablePro/Core/SchemaTracking/StructureChangeManager.swift

@@ -96,9 +96,10 @@ final class StructureChangeManager {
         // Reset working state
         resetWorkingState()
 
-        // Clear changes
+        // Clear changes and undo history
         pendingChanges.removeAll()
         validationErrors.removeAll()
+        undoManager.removeAllActions()
         hasChanges = false
 
         // Increment reloadVersion to trigger DataGridView column width recalculation
@@ -673,8 +674,9 @@ final class StructureChangeManager {
             }
 
         case .primaryKeyChange(let old, _):
+            let current = workingPrimaryKey
             undoManager.registerUndo(withTarget: self) { target in
-                target.applySchemaUndo(.primaryKeyChange(old: self.workingPrimaryKey, new: old))
+                target.applySchemaUndo(.primaryKeyChange(old: current, new: old))
             }
             undoManager.setActionName(String(localized: "Change Primary Key"))
             workingPrimaryKey = old