fix(rte): Deduplicate Tiptap extensions to prevent duplicate name warnings

When multiple Umbraco extensions (e.g., BulletList and OrderedList) include
the same Tiptap extension (ListItem), duplicates were added to the extensions
array, causing Tiptap to log warnings. This change uses a Map to deduplicate
extensions by their name property before passing them to the Editor.

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

Co-Authored-By: Claude <[email protected]>

Author: 2 people

src/Umbraco.Web.UI.Client/src/packages/tiptap/components/input-tiptap/input-tiptap.element.ts

@@ -1,6 +1,6 @@
 import { Editor } from '../../externals.js';
 import { UmbTiptapRteContext } from '../../contexts/tiptap-rte.context.js';
-import type { Extensions } from '../../externals.js';
+import type { AnyExtension } from '../../externals.js';
 import type { UmbTiptapExtensionApi } from '../../extensions/types.js';
 import type { UmbTiptapStatusbarValue, UmbTiptapToolbarValue } from '../types.js';
 import {
@@ -156,12 +156,16 @@ export class UmbInputTiptapElement extends UmbFormControlMixin<string, typeof Um
 		this._toolbar = this.configuration?.getValueByAlias<UmbTiptapToolbarValue>('toolbar') ?? [[[]]];
 		this._statusbar = this.configuration?.getValueByAlias<UmbTiptapStatusbarValue>('statusbar') ?? [];
 
-		const tiptapExtensions: Extensions = [];
+		const tiptapExtensions = new Map<string, AnyExtension>();
 
 		this._extensions.forEach((ext) => {
 			const tiptapExt = ext.getTiptapExtensions({ configuration: this.configuration });
 			if (tiptapExt?.length) {
-				tiptapExtensions.push(...tiptapExt);
+				tiptapExt.forEach((extension) => {
+					if (!tiptapExtensions.has(extension.name)) {
+						tiptapExtensions.set(extension.name, extension);
+					}
+				});
 			}
 
 			const styles = ext.getStyles();
@@ -179,7 +183,7 @@ export class UmbInputTiptapElement extends UmbFormControlMixin<string, typeof Um
 					'aria-required': this.required ? 'true' : 'false',
 				},
 			},
-			extensions: tiptapExtensions,
+			extensions: Array.from(tiptapExtensions.values()),
 			content: this.#value,
 			injectCSS: false, // Prevents injecting CSS into `window.document`, as it never applies to the shadow DOM. [LK]
 			//enableContentCheck: true,