fix: adjust content inset behavior for macOS (#2806)

Fix content inset adjustments for macOS ScrollView.

<!-- Thanks for submitting a pull request! We appreciate you spending
the time to work on these changes. Please provide enough information so
that others can review your pull request. The four fields below are
mandatory. -->

<!-- This fork of react-native provides React Native for macOS for the
community. It also contains some changes that are required for usage
internal to Microsoft. We are working on reducing the diff between
Facebook's public version of react-native and our
microsoft/react-native-macos fork. Long term, we want this fork to only
contain macOS concerns and have the other iOS and Android concerns
contributed upstream.

If you are making a new change then one of the following should be done:
- Consider if it is possible to achieve the desired behavior without
making a change to microsoft/react-native-macos. Often a change can be
made in a layer above in facebook/react-native instead.
- Create a corresponding PR against
[facebook/react-native](https://github.com/facebook/react-native)
**Note:** Ideally you would wait for Facebook feedback before submitting
to Microsoft, since we want to ensure that this fork doesn't deviate
from upstream.
-->

## Summary:

<!-- Explain the **motivation** for making this change. What existing
problem does the pull request solve? -->

## Test Plan:

<!-- Demonstrate the code is solid. Example: The exact commands you ran
and their output, screenshots / videos if the pull request changes the
user interface. -->

---------

Co-authored-by: Saad Najmi <sanajmi@microsoft.com>

Author: eadron

packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTEnhancedScrollView.mm

@@ -41,7 +41,13 @@ - (instancetype)initWithFrame:(CGRect)frame
     // because this attribute affects a position of vertical scrollbar; we don't want this
     // scrollbar flip because we also flip it with whole `UIScrollView` flip.
     self.semanticContentAttribute = UISemanticContentAttributeForceLeftToRight;
-#endif // [macOS]
+#else // [macOS
+    // Similar to iOS's contentInsetAdjustmentBehavior fix
+    // For example: When using NSWindowStyleMaskFullSizeContentView (hidden title bar) and ScrollView as root,
+    // NSScrollView.automaticallyAdjustsContentInsets (default YES) adds contentInset.top to push content below the toolbar.
+    // However, React Native doesn't know about this native contentInset adjustments,causing some caltulation issues  
+    self.automaticallyAdjustsContentInsets = NO;
+#endif // macOS]
 
     __weak __typeof(self) weakSelf = self;
     _delegateSplitter = [[RCTGenericDelegateSplitter alloc] initWithDelegateUpdateBlock:^(id delegate) {