fix(fabric): fix Text overflow in ScrollView on first render (macOS) (#2880)

## Summary

- Add a `layoutSubviews` override in `RCTScrollViewComponentView` on
macOS that resets the `_containerView` (documentView) frame to
`_contentSize` after AppKit's autoresizing corrupts it
- This fixes massive horizontal and vertical overflow when Text is
nested inside a ScrollView on the first render

## Root Cause

On macOS, the `_containerView` serves as the `NSScrollView`'s
`documentView`, whose frame **directly determines the scrollable content
area** (unlike iOS where `UIScrollView.contentSize` is a separate
property).

React's layout system explicitly manages `_containerView.frame` via
`updateState:` to match the content bounding rect. However,
`autoresizingMask` caused AppKit to **also** resize the container
whenever the `NSClipView` resized (e.g., during initial `tile` after
mounting). This added the clip view's size delta to the container's
dimensions, inflating it well beyond the correct content size.

The `layoutSubviews` override runs after AppKit's layout pass (which
triggers autoresizing), so it reliably corrects the frame back to the
React-managed `_contentSize`.

The issue self-corrects on window resize because the size change
triggers a React re-layout that overwrites the corrupted frame with
fresh measurements.

## Test plan

| Before (bug) | After (fix) |
|---|---|
| <img
src="https://github.com/user-attachments/assets/6a63357e-6dd3-4f69-b134-2d0f78c5b995"
/> | <img
src="https://github.com/user-attachments/assets/5678e2ad-bc40-4987-aaa3-5854c809649e"
/> |





Fixes #2857

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: Saadnajmi

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

@@ -184,6 +184,30 @@ - (void)dealloc
 #endif // [macOS]
 }
 
+#if TARGET_OS_OSX // [macOS
+- (void)layoutSubviews
+{
+  [super layoutSubviews];
+
+  // On macOS, the _containerView is the NSScrollView's documentView and has autoresizingMask set so
+  // it fills the visible area before React's first layout pass. However, AppKit's autoresizing can
+  // corrupt the documentView's frame by adding the NSClipView's size delta to the container's
+  // dimensions (e.g., during initial tile or window resize), inflating it well beyond the correct
+  // content size. This produces massive horizontal and vertical overflow on first render.
+  //
+  // After React has set the content size via updateState:, we reset the documentView frame here to
+  // undo any autoresizing corruption. This runs after AppKit's layout (which triggers autoresizing),
+  // so it reliably corrects the frame.
+  if (!CGSizeEqualToSize(_contentSize, CGSizeZero)) {
+    CGRect containerFrame = _containerView.frame;
+    if (!CGSizeEqualToSize(containerFrame.size, _contentSize)) {
+      containerFrame.size = _contentSize;
+      _containerView.frame = containerFrame;
+    }
+  }
+}
+#endif // macOS]
+
 #if TARGET_OS_IOS
 - (void)_registerKeyboardListener
 {