fix(content-renderer): preserve class methods when merging renderers

Event-card-root was spreading ContentRenderer into a plain object,
which lost all class methods like getKindHandler(). This caused
"getKindHandler is not a function" errors in embedded-event.

Solution:
- Add clone() method to ContentRenderer that properly duplicates
  all handlers, components, and priorities
- Update event-card-root to use clone() instead of spread operator
- Fall back to defaultContentRenderer instead of empty object

Author: pablof7z

svelte/registry/src/lib/registry/components/event-card/event-card-root.svelte

@@ -4,12 +4,13 @@
   import { getContext, setContext } from 'svelte';
   import { EVENT_CARD_CONTEXT_KEY, type EventCardContext } from './event-card.context.js';
   import { CONTENT_RENDERER_CONTEXT_KEY, type ContentRendererContext } from '../../ui/content-renderer/content-renderer.context.js';
-  import type {
-    UserClickCallback,
-    EventClickCallback,
-    HashtagClickCallback,
-    LinkClickCallback,
-    MediaClickCallback
+  import {
+    defaultContentRenderer,
+    type UserClickCallback,
+    type EventClickCallback,
+    type HashtagClickCallback,
+    type LinkClickCallback,
+    type MediaClickCallback
   } from '../../ui/content-renderer/index.svelte.js';
   import { getNDK } from '../../utils/ndk';
   import { cn } from '../../utils/cn';
@@ -67,17 +68,23 @@
   // Get parent ContentRendererContext if it exists
   const parentRendererContext = getContext<ContentRendererContext | undefined>(CONTENT_RENDERER_CONTEXT_KEY);
 
-  // Create a renderer that merges parent renderer with local callbacks
+  // Create a renderer that clones parent renderer with overridden callbacks
   const renderer = $derived.by(() => {
-    const base = parentRendererContext?.renderer ?? {} as any;
-    return {
-      ...base,
-      onUserClick: onUserClick ?? base.onUserClick,
-      onEventClick: onEventClick ?? base.onEventClick,
-      onHashtagClick: onHashtagClick ?? base.onHashtagClick,
-      onLinkClick: onLinkClick ?? base.onLinkClick,
-      onMediaClick: onMediaClick ?? base.onMediaClick
-    };
+    const base = parentRendererContext?.renderer ?? defaultContentRenderer;
+
+    // If no callbacks to override, return base as-is
+    if (!onUserClick && !onEventClick && !onHashtagClick && !onLinkClick && !onMediaClick) {
+      return base;
+    }
+
+    // Clone the renderer with overridden callbacks
+    return base.clone({
+      onUserClick,
+      onEventClick,
+      onHashtagClick,
+      onLinkClick,
+      onMediaClick
+    });
   });
 
   // ContentRendererContext: provide the merged renderer

svelte/registry/src/lib/registry/ui/content-renderer/index.svelte.ts

@@ -363,6 +363,49 @@ export class ContentRenderer {
 		this.mediaPriority = 0;
 		this.fallbackPriority = 0;
 	}
+
+	/**
+	 * Create a clone of this renderer with all handlers and components
+	 * Optionally override click callbacks
+	 */
+	clone(callbacks?: {
+		onUserClick?: UserClickCallback;
+		onEventClick?: EventClickCallback;
+		onHashtagClick?: HashtagClickCallback;
+		onLinkClick?: LinkClickCallback;
+		onMediaClick?: MediaClickCallback;
+	}): ContentRenderer {
+		const cloned = new ContentRenderer();
+
+		// Copy all public properties
+		cloned.blockNsfw = this.blockNsfw;
+		cloned.mentionComponent = this.mentionComponent;
+		cloned.hashtagComponent = this.hashtagComponent;
+		cloned.linkComponent = this.linkComponent;
+		cloned.mediaComponent = this.mediaComponent;
+		cloned.fallbackComponent = this.fallbackComponent;
+
+		// Copy callbacks (use provided overrides or original values)
+		cloned.onUserClick = callbacks?.onUserClick ?? this.onUserClick;
+		cloned.onEventClick = callbacks?.onEventClick ?? this.onEventClick;
+		cloned.onHashtagClick = callbacks?.onHashtagClick ?? this.onHashtagClick;
+		cloned.onLinkClick = callbacks?.onLinkClick ?? this.onLinkClick;
+		cloned.onMediaClick = callbacks?.onMediaClick ?? this.onMediaClick;
+
+		// Copy all handlers from the private map
+		for (const [kind, info] of this.handlers) {
+			cloned.handlers.set(kind, info);
+		}
+
+		// Copy priorities
+		cloned.mentionPriority = this.mentionPriority;
+		cloned.hashtagPriority = this.hashtagPriority;
+		cloned.linkPriority = this.linkPriority;
+		cloned.mediaPriority = this.mediaPriority;
+		cloned.fallbackPriority = this.fallbackPriority;
+
+		return cloned;
+	}
 }
 
 /**