refactor(ios): rename textAlignVertical bridge and add Auto fast-path

Rename the ObjC property to `textAlignVertical` so the bridge matches
the JS prop and the C++ paragraph attribute exactly. The enum type stays
`RCTUITextViewTextAlignmentVertical` since it mirrors the C++ enum
class name.

Skip the contentSize read for the default Auto / Top case so the new
code adds zero per-layout work for apps that don't opt in.

Author: quantizor

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

@@ -55,7 +55,7 @@ typedef NS_ENUM(NSInteger, RCTUITextViewTextAlignmentVertical) {
  * multiline value can sit centered or pushed to the bottom of a tall fixed
  * frame. Defaults to `Auto` (top-aligned, current behavior).
  */
-@property (nonatomic, assign) RCTUITextViewTextAlignmentVertical textAlignmentVertical;
+@property (nonatomic, assign) RCTUITextViewTextAlignmentVertical textAlignVertical;
 
 @property (nonatomic, strong, nullable) NSString *inputAccessoryViewID;
 @property (nonatomic, strong, nullable) NSString *inputAccessoryViewButtonLabel;

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

@@ -150,12 +150,12 @@ - (void)textDidChange
   [self _invalidatePlaceholderVisibility];
 }
 
-- (void)setTextAlignmentVertical:(RCTUITextViewTextAlignmentVertical)textAlignmentVertical
+- (void)setTextAlignVertical:(RCTUITextViewTextAlignmentVertical)textAlignVertical
 {
-  if (_textAlignmentVertical == textAlignmentVertical) {
+  if (_textAlignVertical == textAlignVertical) {
     return;
   }
-  _textAlignmentVertical = textAlignmentVertical;
+  _textAlignVertical = textAlignVertical;
   [self setNeedsLayout];
 }
 
@@ -306,25 +306,28 @@ - (void)layoutSubviews
 // by RN's existing wiring (only `textContainerInset` is set externally).
 - (void)_applyVerticalAlignmentInset
 {
+  // Fast path for apps that don't use the feature: skip the contentSize read.
+  if (_textAlignVertical == RCTUITextViewTextAlignmentVerticalAuto ||
+      _textAlignVertical == RCTUITextViewTextAlignmentVerticalTop) {
+    if (self.contentInset.top != 0) {
+      UIEdgeInsets contentInset = self.contentInset;
+      contentInset.top = 0;
+      self.contentInset = contentInset;
+    }
+    return;
+  }
   CGFloat boundsHeight = CGRectGetHeight(self.bounds);
   CGFloat contentHeight = self.contentSize.height;
   CGFloat topInset = 0;
   if (boundsHeight > contentHeight) {
-    switch (_textAlignmentVertical) {
-      case RCTUITextViewTextAlignmentVerticalCenter:
-        topInset = (boundsHeight - contentHeight) / 2;
-        break;
-      case RCTUITextViewTextAlignmentVerticalBottom:
-        topInset = boundsHeight - contentHeight;
-        break;
-      case RCTUITextViewTextAlignmentVerticalAuto:
-      case RCTUITextViewTextAlignmentVerticalTop:
-        topInset = 0;
-        break;
+    if (_textAlignVertical == RCTUITextViewTextAlignmentVerticalCenter) {
+      topInset = (boundsHeight - contentHeight) / 2;
+    } else if (_textAlignVertical == RCTUITextViewTextAlignmentVerticalBottom) {
+      topInset = boundsHeight - contentHeight;
     }
   }
-  UIEdgeInsets contentInset = self.contentInset;
-  if (contentInset.top != topInset) {
+  if (self.contentInset.top != topInset) {
+    UIEdgeInsets contentInset = self.contentInset;
     contentInset.top = topInset;
     self.contentInset = contentInset;
   }

packages/react-native/React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm

@@ -200,7 +200,7 @@ - (void)updateProps:(const Props::Shared &)props oldProps:(const Props::Shared &
   if (newTextInputProps.multiline &&
       newTextInputProps.paragraphAttributes.textAlignVertical !=
           oldTextInputProps.paragraphAttributes.textAlignVertical) {
-    [self _applyTextAlignmentVerticalToMultilineView:newTextInputProps.paragraphAttributes.textAlignVertical];
+    [self _applyTextAlignVerticalToMultilineView:newTextInputProps.paragraphAttributes.textAlignVertical];
   }
 
   if (newTextInputProps.traits.autocapitalizationType != oldTextInputProps.traits.autocapitalizationType) {
@@ -838,14 +838,14 @@ - (void)_setMultiline:(BOOL)multiline
 
   if (multiline) {
     const auto &textInputProps = static_cast<const TextInputProps &>(*_props);
-    [self _applyTextAlignmentVerticalToMultilineView:textInputProps.paragraphAttributes.textAlignVertical];
+    [self _applyTextAlignVerticalToMultilineView:textInputProps.paragraphAttributes.textAlignVertical];
   }
 }
 
 // Single-line `UITextField` centers its content vertically inside the field
 // frame natively, so this routing is only meaningful when the backed view is
 // the multiline `RCTUITextView`. UITextField callers no-op.
-- (void)_applyTextAlignmentVerticalToMultilineView:
+- (void)_applyTextAlignVerticalToMultilineView:
     (const std::optional<facebook::react::TextAlignmentVertical> &)textAlignVertical
 {
   if (![_backedTextInputView isKindOfClass:[RCTUITextView class]]) {
@@ -868,7 +868,7 @@ - (void)_applyTextAlignmentVerticalToMultilineView:
         break;
     }
   }
-  ((RCTUITextView *)_backedTextInputView).textAlignmentVertical = mapped;
+  ((RCTUITextView *)_backedTextInputView).textAlignVertical = mapped;
 }
 
 - (void)_setShowSoftInputOnFocus:(BOOL)showSoftInputOnFocus