fix: clear usage interval in finally so it cannot leak on send failure (#25478)

getChatEventEmitter starts a setInterval emitting a `usage` socket event
every second; clearInterval ran only after sendMessageSocket resolved, so
any throw/reject left the interval firing for the page lifetime. Each
failed send added another orphaned interval, inflating server-side usage
accounting and growing CPU/memory over a session.

Wrap the send in try/finally so the interval is always cleared, on both
the happy path and any thrown/rejected path. The exception still
propagates unchanged.

Fixes #25465

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/components/chat/Chat.svelte

@@ -2159,6 +2159,7 @@
 		if (primaryModel && primaryResponseMessageId) {
 			const chatEventEmitter = await getChatEventEmitter(primaryModel.id, _chatId);
 
+			try {
 				scrollToBottom();
 				await sendMessageSocket(
 					primaryModel,
@@ -2173,9 +2174,10 @@
 						regenerationPrompt
 					}
 				);
-
+			} finally {
 				if (chatEventEmitter) clearInterval(chatEventEmitter);
 			}
+		}
 	};
 
 	const getFeatures = () => {