fix(chat): use code block language tag to detect Vega-Lite specs for rendering (#25843)

src/lib/components/chat/Messages/CodeBlock.svelte

@@ -379,7 +379,7 @@
 			(token?.raw ?? '').slice(-4).includes('```')
 		) {
 			try {
-				renderHTML = await renderVegaVisualization(code);
+				renderHTML = await renderVegaVisualization(code, lang);
 			} catch (error) {
 				console.error('Failed to render Vega visualization:', error);
 				const errorMsg = error instanceof Error ? error.message : String(error);