Rename TypeSafe and LangChain Jev spans from evaluate to decide #25249

Follow getsentry/sentry-conventions#696: gen_ai.evaluate is deprecated in favor of gen_ai.decide.

The TypeSafe integration (src/ai/typesafe/) makes the span for TypeSafeClient.systemOne(). The LangChain integration uses the same startEvaluateSpan() for TypeSafeClassifier runs and for Jev middleware calls inside createAgent / LangGraph. So one change covers all three paths.

Target span

• Name: decide <model> (was evaluate <model>)
• Op: gen_ai.decide (was gen_ai.evaluate)
• gen_ai.operation.name: decide (was evaluate)
• No other change. gen_ai.input.messages / gen_ai.output.messages keep type: 'evaluation'.

Scope

• packages/server-utils/src/ai/typesafe/index.ts and src/ai/langchain/typesafe-classifier.ts. Rename startEvaluateSpan and related helpers to match.
• Update the tests: node-integration-tests suites typesafe, langchain/v1, langgraph/v1; cloudflare-integration-tests suite langchain-typesafe-classifier; unit test test/ai/lib/tracing/langchain-invoke-agent.test.ts.