fix(openai-agents): End child spans on trace end (#1813)

Supersedes
#1361

Ends child spans of an openai agents trace before ending the root span -
making sure that all the spans in the trace are properly ended.

Author: lforst

.changeset/lazy-dots-send.md

@@ -0,0 +1,5 @@
+---
+"braintrust": patch
+---
+
+fix(openai-agents): End child spans on trace end

integrations/openai-agents-js/src/index.ts

@@ -322,6 +322,11 @@ export class OpenAIAgentsTraceProcessor {
     const traceData = this.traceSpans.get(trace.traceId);
 
     if (traceData) {
+      for (const [spanId, braintrustSpan] of traceData.childSpans) {
+        braintrustSpan.end();
+        traceData.childSpans.delete(spanId);
+      }
+
       try {
         traceData.rootSpan.log({
           input: traceData.metadata.firstInput,