Defer transformed TextInput edits outside UIKit delegate callbacks (#59188)

Summary:
Pull Request resolved: #59188

UIKit text change delegate callbacks now remain decision-only when JavaScript transforms an edit. The adapter rejects UIKit's original 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.

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

Reviewed By: cipolleschi

Differential Revision: D126057002

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
 {