ui: make editedContent a so background recompute does not wipe in-progress edits

Author: ServeurpersoCom

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessage/ChatMessage.svelte

@@ -43,7 +43,7 @@
 		assistantMessages: number;
 		messageTypes: string[];
 	} | null>(null);
-	let editedContent = $derived(message.content);
+	let editedContent = $state(message.content);
 
 	let rawEditContent = $derived.by(() => {
 		if (message.role !== MessageRole.ASSISTANT) return undefined;