Add GHCP telemetry correlation fields for tool responses and response turns

[tbogoodnews]

Summary

Adds correlation fields to GHCP agent.tool.responseLength telemetry and reports the current turn on response.success telemetry.

Problem

The GHCP agent.tool.responseLength event only emitted toolName and tokenCount, making it difficult to correlate individual tool result token usage with a chat conversation, request, or model.

response.success did not include the current turn value, which made response-level telemetry harder to align with request-level telemetry for a conversation.

Changes

toolCalling.tsx

• Extends sendInvokedToolTelemetry() to accept request-scoped telemetry properties
• Emits conversationId, requestId, and model on agent.tool.responseLength
• Uses promptContext.conversation?.sessionId for conversationId so it matches the conversation session used by panel.request
• Adds GDPR classifications for conversationId, requestId, and model

chatVariables.tsx

• Passes conversationId and requestId through for tool references invoked from chat variables

toolCalling.spec.ts

• Updates the existing tool result telemetry test to verify:
  • conversationId
  • requestId
  • model
  • toolName
  • tokenCount measurement

chatMLFetcherTelemetry.ts

• Adds turn to response.success measurements
• Reports the existing turn value from base telemetry without incrementing it
• Adds GDPR classification for turn

Validation

• Copilot TypeScript check passed
• Focused toolCalling.spec.ts test passed
• Full Copilot unit suite was run; the telemetry test passed, with unrelated existing/environment failures outside this change

Related issue

https://github.com/microsoft/vscode-internalbacklog/issues/7765

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[tbogoodnews]

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