Defer transformed TextInput edits outside UIKit delegate callbacks (#59239)

Summary:
Pull Request resolved: #59239

UIKit text change delegate callbacks now remain decision-only when JavaScript transforms an edit. The adapter rejects the original UIKit edit, records an implementation-private transaction, and applies an incremental `UITextInput` replacement on the next main-queue turn after validating the backing-view generation and base text.

This preserves partial `maxLength` truncation without synchronously replacing the full attributed string or selection. Marked-text composition remains UIKit-owned; an over-limit committed value is corrected through the same deferred transaction path after composition ends. A runtime gate controls the new path.

Stale edits are discarded when the backing text changes, lifecycle and JavaScript-driven updates invalidate queued transactions, and successful commits emit one change update plus the corresponding selection event. On tvOS, the deferred drain remains disabled because multiline text views are not editable.

Changelog:
[iOS][Fixed] - Preserve transformed `TextInput` edits without synchronously rewriting text inside UIKit delegate callbacks

Differential Revision: D126438495

Author: javache

packages/react-native/Libraries/Text/React-RCTText.podspec

@@ -34,6 +34,7 @@ Pod::Spec.new do |s|
 
   s.dependency "Yoga"
   s.dependency "React-Core/RCTTextHeaders", version
+  add_dependency(s, "React-featureflags")
 
   mark_as_react_native_build(s)
 end

packages/react-native/Libraries/Text/TextInput/Multiline/RCTUITextView.mm

@@ -12,6 +12,11 @@
 
 #import <React/RCTBackedTextInputDelegateAdapter.h>
 
+@interface RCTBackedTextViewDelegateAdapter (PendingTextInputEdit)
+- (void)invalidatePendingTextInputEdit;
+- (void)schedulePendingTextInputEditWithRange:(NSRange)range replacementText:(NSString *)replacementText;
+@end
+
 @implementation RCTUITextView {
   UILabel *_placeholderView;
   UITextView *_detachedTextView;
@@ -207,6 +212,16 @@ - (void)setSelectedTextRange:(UITextRange *)selectedTextRange notifyDelegate:(BO
   [super setSelectedTextRange:selectedTextRange];
 }
 
+- (void)rct_invalidatePendingTextInputEdit
+{
+  [_textInputDelegateAdapter invalidatePendingTextInputEdit];
+}
+
+- (void)rct_enqueueTextInputEditWithRange:(NSRange)range replacementText:(NSString *)replacementText
+{
+  [_textInputDelegateAdapter schedulePendingTextInputEditWithRange:range replacementText:replacementText];
+}
+
 // After restoring the previous cursor position, we manually trigger the scroll to the new cursor position (PR 38679).
 - (void)scrollRangeToVisible:(NSRange)range
 {