Handle streamed Responses API compaction items

[dileepyavan]

Summary

• Detect compaction items at the top of OpenAIResponsesProcessor.push across stream events that carry either item or response.output.
• Capture and emit compaction items from intermediate events such as response.output_item.added, not only response.output_item.done/response.completed.
• Preserve final response.completed reconciliation so the latest final compaction item is still used when it differs from an earlier streamed item.
• Add regression coverage that an early/intermediate compaction item is round-tripped into the next Responses API request.

Validation

• cd extensions/copilot && npm run test:unit -- src/platform/endpoint/node/test/responsesApi.spec.ts
• Result: 26 passed

Notes

• Debug logging added during investigation was removed before this PR.
• Untracked local dotfiles in the workspace were not included in the commit.

[github-actions]

Screenshot Changes

Base: 182bcf49 Current: 782dc850

Changed (3)

editor/inlineCompletions/other/JumpToHint/Dark

Before	After

agentSessionsViewer/WithMarkdownBadge/Light

Before	After

agentSessionsViewer/WithMarkdownBadge/Dark

Before	After

[Copilot]

Pull request overview

This PR updates the Copilot extension’s OpenAI Responses API stream processing to detect and emit context-compaction items earlier in the stream (e.g. response.output_item.added), ensuring those items can be round-tripped into the next request even when they arrive before output_item.done/response.completed.

Changes:

• Detect compaction items from both streamed item events and events containing response.output, emitting compaction deltas as soon as they appear.
• Preserve response.completed reconciliation so the final compaction item still wins when it differs from earlier streamed items.
• Add regression tests ensuring early/intermediate compaction items are captured and included in the next request body.

Show a summary per file

File	Description
extensions/copilot/src/platform/endpoint/node/responsesApi.ts	Adds compaction extraction from additional stream shapes and emits compaction deltas earlier while keeping final reconciliation.
extensions/copilot/src/platform/endpoint/node/test/responsesApi.spec.ts	Adds coverage for compaction items arriving before output_item.done and updates an existing reconciliation test to include output_item.added.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1