perf: skip artifact extraction during streaming to prevent UI freezes

Author: Algorithm5838

src/lib/components/chat/Chat.svelte

@@ -863,7 +863,11 @@
 	};
 
 	$: if (history) {
-		getContents();
+		// Skip artifact extraction during streaming to avoid expensive regex
+		// on the entire chat history for every incoming chunk
+		if (!generating) {
+			getContents();
+		}
 	} else {
 		artifactContents.set([]);
 	}