Fix usage logging dedupe and reduce stats churn

- batch console log buffer events and support batched SSE log messages
- debounce usage stats update/pending events to reduce UI/runtime churn
- avoid awaiting request-success bookkeeping before returning provider responses
- deduplicate identical usage writes in usageHistory/daily aggregates
- reduce default logger verbosity from DEBUG to INFO (overridable via LOG_LEVEL)

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/handlers/chatCore/streamingHandler.js

@@ -44,7 +44,13 @@ function buildTransformStream({ provider, sourceFormat, targetFormat, userAgent,
  * Handle streaming response — pipe provider SSE through transform stream to client.
  */
 export function handleStreamingResponse({ providerResponse, provider, model, sourceFormat, targetFormat, userAgent, body, stream, translatedBody, finalBody, requestStartTime, connectionId, apiKey, clientRawRequest, onRequestSuccess, reqLogger, toolNameMap, streamController, onStreamComplete }) {
-  if (onRequestSuccess) onRequestSuccess();
+  if (onRequestSuccess) {
+    Promise.resolve()
+      .then(onRequestSuccess)
+      .catch(err => {
+        console.error("[ChatCore] onRequestSuccess failed:", err?.message || err);
+      });
+  }
 
   const transformStream = buildTransformStream({ provider, sourceFormat, targetFormat, userAgent, reqLogger, toolNameMap, model, connectionId, body, onStreamComplete, apiKey });