fix: upsert traces to handle duplicate IDs from intermediate flushes

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-Claude)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

packages/sdk-ts/src/transport.ts

@@ -27,7 +27,12 @@ export class BatchTransport {
   }
 
   add(trace: TracePayload): void {
-    this.buffer.push(trace);
+    const idx = this.buffer.findIndex((t) => t.id === trace.id);
+    if (idx !== -1) {
+      this.buffer[idx] = trace;
+    } else {
+      this.buffer.push(trace);
+    }
     if (this.buffer.length >= this.maxBatchSize) {
       void this._doFlush();
     }