fix: reset taskIds and messageQueue on new chat (#21731)

fix: reset taskIds and messageQueue on new chat

Fixes a bug where clicking "New Chat" after sending a message would
silently drop subsequent messages. The initNewChat function reset most
chat state but did not clear taskIds or messageQueue, causing
submitPrompt to queue messages indefinitely instead of sending them.

src/lib/components/chat/Chat.svelte

@@ -1065,6 +1065,8 @@
 
 		chatFiles = [];
 		params = {};
+		taskIds = null;
+		messageQueue = [];
 
 		if ($page.url.searchParams.get('youtube')) {
 			await uploadWeb(`https://www.youtube.com/watch?v=${$page.url.searchParams.get('youtube')}`);