vercelAIIntegration: Record runtimeContext and toolContext on AI SDK v7 spans #25352

Part of #24706 (#24706).

ai@7.0.114 filters runtimeContext and toolContext on the tracing channel by telemetry.includeRuntimeContext / includeToolsContext (vercel/ai#21447). The v7 subscriber (packages/server-utils/src/integrations/vercel-ai/vercel-ai-dc-subscriber.ts) does not read these fields yet.

Scope:

• Set vercel.ai.settings.runtimeContext.<key> on the invoke_agent span for each key in event.runtimeContext.
• Copy the same attributes to the child generate_content and execute_tool spans. Use the callId maps, because the child events do not carry runtimeContext.
• Record event.toolContext on execute_tool spans.
• Do not read these fields on ai < 7.0.114. Those versions send unfiltered context, which can contain secrets.

Done when:

• Integration tests on ai@>=7.0.114 show that included keys are on all 3 span types and excluded keys are not.
• A test on ai@7.0.113 (or a guard test) shows that no context attributes are set.

Open question: How do we detect the version? We can check the ai version or the event shape, or we can add a new min version for the v7 subscriber.