Update to Responses API compaction and telemetry

[dileepyavan]

Summary

• Ensure previous responseId is being passed when ignoreStatefulMarker is false.
• add server-side compaction outcome telemetry and regression coverage for enabled and disabled compaction flows

Details

• createResponsesRequestBody now computes the compaction threshold once and uses it to gate both request context_management and websocket stateful-marker slicing behavior
• websocket and pass-through OpenAIResponsesProcessor call sites now receive the request compaction threshold from the request body
• responsesApi.compactionOutcome emits only when compaction is enabled and reports the outcome, request IDs, model, threshold, and token counts
• compaction telemetry intentionally does not include completionId or compactionMessageId

Testing

• runTests on src/platform/endpoint/node/test/responsesApi.spec.ts (16 passed)
• verified start-watch-tasks output showed no compile errors

[Copilot]

Pull request overview

This PR refines how the OpenAI Responses API “context-management compaction” feature is enabled and observed, ensuring compaction-specific behavior only runs when compaction is actually enabled and adding outcome telemetry plus regression coverage.

Changes:

• Centralizes computation of the compaction threshold and uses it to gate request context_management and WebSocket stateful-marker slicing.
• Propagates the compaction threshold into Responses API stream processors (HTTP, WebSocket, and pass-through) and emits responsesApi.compactionOutcome telemetry only when compaction is enabled.
• Adds unit tests covering enabled/disabled compaction flows and telemetry emission behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/platform/networking/node/chatStream.ts	Adds responsesApi.compactionOutcome telemetry emitter helper with GDPR annotation.
src/platform/endpoint/node/responsesApi.ts	Computes compaction threshold once, adjusts marker/compaction slicing, plumbs threshold into processor, and emits compaction outcome telemetry.
src/platform/endpoint/node/chatEndpoint.ts	Passes computed compaction threshold through to Responses API response processing.
src/extension/prompt/node/chatMLFetcher.ts	Ensures WebSocket Responses API processing receives compaction threshold parsed from request body.
src/extension/externalAgents/node/oaiLanguageModelServer.ts	Ensures pass-through Responses API processing receives compaction threshold parsed from request body.
src/platform/endpoint/node/test/responsesApi.spec.ts	Adds tests for request-body threshold extraction, WebSocket slicing behavior, and compaction telemetry emission gating.
.vscode/settings.json	Enables terminal tool sandbox in workspace settings.
.vscode/launch.json	Adds preLaunchTask: "compile" to the primary extension launch configuration.