Add support for vercel `ToolLoopAgent`

docs: [https://ai-sdk.dev/docs/agents/overview#toolloopagent-class](<https://ai-sdk.dev/docs/agents/overview#toolloopagent-class>)

[Internally](<https://github.com/vercel/ai/blob/main/packages/ai/src/agent/tool-loop-agent.ts#L132>) this calls `generateText` so the core span processing logic should hopefully transfer to this, but the patching logic will need some special handling.