Capture Jev middleware calls inside LangGraph / createAgent #25032

LangChain's Jev middleware (model router and auto-mode) runs inside agents. Our LangChain/LangGraph instrumentation skips chain spans inside agents, so these Jev calls are probably invisible.

This comes from reading the code. It is not verified at runtime yet.

Fix

• Reproduce with a createAgent / LangGraph agent that uses the Jev middleware and confirm the gap.
• If confirmed, record these calls as gen_ai.evaluate spans and add a test.

Checked against sentry-javascript at b126416 (v11.4.0).