feat(executor): share SSE usage filtering across streams

internal/runtime/executor/antigravity_executor.go

@@ -167,6 +167,11 @@ func (e *AntigravityExecutor) ExecuteStream(ctx context.Context, auth *cliproxya
 		for scanner.Scan() {
 			line := scanner.Bytes()
 			appendAPIResponseChunk(ctx, e.cfg, line)
+
+			// Filter usage metadata for all models
+			// Only retain usage statistics in the terminal chunk
+			line = FilterSSEUsageMetadata(line)
+
 			chunks := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, bytes.Clone(line), &param)
 			for i := range chunks {
 				out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunks[i])}