WithRunNameContext sets the span (run) name for the next traced request made with ctx.
func WithRunNameContext(ctx context.Context, name string) context.ContextWithRunNameContext sets the span (run) name for the next traced request made with ctx. The run name in LangSmith is the OTLP span name; there is no separate field. Use this so one client can emit runs with different names per call, e.g. in tests:
ctx = traceanthropic.WithRunNameContext(ctx, "anthropic_nonstreaming") client.Messages.New(ctx, ...)