Vercel AI V6 class-based agents have incorrect `gen_ai.operation.name` mapping

[nicohrubec]

V6's ToolLoopAgent with functionId set causes operation.name to be ai.streamText myAgent instead of ai.streamText. The exact-match lookup in mapVercelAiOperationName misses this, leaving gen_ai.operation.name as the raw Vercel value instead of invoke_agent. Same issue affects child generate_content and execute_tool spans. Function-based usage without functionId is unaffected.

[linear-code]

JS-2162

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #20285, which was included in the 10.49.0 release.