[Luca Forstner (lforst)]

• Add tracing for @ai-sdk/code-mode, capturing executed JavaScript and nesting the functions it calls underneath the execution.
• Extend wrapAISDK to trace direct code-mode calls without a loader hook:

  import * as codeMode from "@ai-sdk/code-mode";
  import { wrapAISDK } from "braintrust";
  
  // Now supports code-mode execution.
  const { experimental_runCodeMode } = wrapAISDK(codeMode);

• Start tool traces before running the tool so nested calls attach to the correct parent and synchronous errors are captured.
• Avoid duplicate traces when automatic instrumentation and explicit Braintrust telemetry are both enabled.

Example trace: https://www.braintrust.dev/app/Braintrust%20SDKs/p/tmp-luca/logs?r=586cb08b3efce34c640c3f045f83b40a&sid=22ffb096f6fc1e7e&tvt=trace