refactor: extract shared BackButton component from LinkUI

- Create shared BackButton component to eliminate duplication
- Replace duplicated back button implementations in LinkUIBlockInserter and LinkUIPageCreator
- Standardize back button behavior and styling across components
- Remove unused chevron icon imports from page-creator.js
- Add proper JSDoc documentation for BackButton component

This is the first phase of LinkUI duplication cleanup as discussed in PR #71163 follow-ups.

Author: getdave

packages/block-library/src/navigation-link/link-ui.js

@@ -33,6 +33,29 @@ import { useInstanceId, useFocusOnMount } from '@wordpress/compose';
 import { unlock } from '../lock-unlock';
 import { LinkUIPageCreator } from './page-creator';
 
+/**
+ * Shared BackButton component for consistent navigation across LinkUI sub-components.
+ *
+ * @param {Object}   props           Component props.
+ * @param {string}   props.className CSS class name for the button.
+ * @param {Function} props.onBack    Callback when user wants to go back.
+ */
+function BackButton( { className, onBack } ) {
+	return (
+		<Button
+			className={ className }
+			icon={ isRTL() ? chevronRightSmall : chevronLeftSmall }
+			onClick={ ( e ) => {
+				e.preventDefault();
+				onBack();
+			} }
+			size="small"
+		>
+			{ __( 'Back' ) }
+		</Button>
+	);
+}
+
 const { PrivateQuickInserter: QuickInserter } = unlock(
 	blockEditorPrivateApis
 );
@@ -118,17 +141,10 @@ function LinkUIBlockInserter( { clientId, onBack, onBlockInsert } ) {
 				</p>
 			</VisuallyHidden>
 
-			<Button
+			<BackButton
 				className="link-ui-block-inserter__back"
-				icon={ isRTL() ? chevronRightSmall : chevronLeftSmall }
-				onClick={ ( e ) => {
-					e.preventDefault();
-					onBack();
-				} }
-				size="small"
-			>
-				{ __( 'Back' ) }
-			</Button>
+				onBack={ onBack }
+			/>
 
 			<QuickInserter
 				rootClientId={ rootBlockClientId }
@@ -272,6 +288,8 @@ function UnforwardedLinkUI( props, ref ) {
 
 export const LinkUI = forwardRef( UnforwardedLinkUI );
 
+export { BackButton };
+
 const LinkUITools = ( {
 	setAddingBlock,
 	setAddingPage,

packages/block-library/src/navigation-link/page-creator.js

@@ -9,14 +9,18 @@ import {
 	__experimentalVStack as VStack,
 	__experimentalHStack as HStack,
 } from '@wordpress/components';
-import { __, isRTL } from '@wordpress/i18n';
+import { __ } from '@wordpress/i18n';
 import { useSelect, useDispatch } from '@wordpress/data';
 import { store as coreStore } from '@wordpress/core-data';
 import { decodeEntities } from '@wordpress/html-entities';
 import { useState } from '@wordpress/element';
-import { chevronLeftSmall, chevronRightSmall } from '@wordpress/icons';
 import { useFocusOnMount } from '@wordpress/compose';
 
+/**
+ * Internal dependencies
+ */
+import { BackButton } from './link-ui';
+
 /**
  * Component for creating new pages within the Navigation Link UI.
  *
@@ -96,17 +100,10 @@ export function LinkUIPageCreator( {
 
 	return (
 		<div className="link-ui-page-creator" ref={ focusOnMountRef }>
-			<Button
+			<BackButton
 				className="link-ui-page-creator__back"
-				icon={ isRTL() ? chevronRightSmall : chevronLeftSmall }
-				onClick={ ( e ) => {
-					e.preventDefault();
-					onBack();
-				} }
-				size="small"
-			>
-				{ __( 'Back' ) }
-			</Button>
+				onBack={ onBack }
+			/>
 
 			<VStack className="link-ui-page-creator__inner" spacing={ 4 }>
 				<form onSubmit={ createPage }>