refactor: extract Responses lifecycle to open-sse/utils/stream/responsesLifecycle.ts (Issue #3594)

[oyi77]

Part of modularization effort (Issue #3594).

Extracts OpenAI Responses API lifecycle handling from the monolithic open-sse/utils/stream.ts into a dedicated module.

Changes:

• New file: open-sse/utils/stream/responsesLifecycle.ts (203 lines)
• Exports: normalizeResponsesSseIds, markPendingRequestCleared, pushUniqueResponsesOutputItems, backfillResponsesCompletedOutput, stripResponsesLifecycleEcho

Testing: No behavior change. Existing stream tests pass.

Follow-up PRs will extract: types (#3917), utils (#3918), errors (#3919), textualToolCalls (#3920), sseFormatters (#3923), openaiChunks (#3924), claudeLifecycle (#3925), and streamCore.

[gemini-code-assist]

Code Review

This pull request introduces a new utility file open-sse/utils/stream/responsesLifecycle.ts to handle OpenAI Responses API stream lifecycle events, including ID normalization, backfilling completed outputs, and stripping request echoes to prevent oversized SSE events. The review feedback highlights two main issues: first, there are unused imports (convertOpenAIToResponsesToolCall and uuidv4) that should be removed; second, according to the repository style guide, adding production code in open-sse/ requires corresponding unit tests to be added in the tests/ directory.

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[gemini-code-assist]

The imports 'convertOpenAIToResponsesToolCall' and 'uuidv4' are not used anywhere in this file. Removing unused imports keeps the codebase clean and prevents potential linter or build errors.

Suggested change

	import { convertOpenAIToResponsesToolCall } from "../handlers/responseTranslator.ts";
	import { v4 as uuidv4 } from "uuid";
	import { stringifyIdValue } from "./utils.ts";
	import { JsonRecord } from "./types.ts";
	import { stringifyIdValue } from "./utils.ts";
	import { JsonRecord } from "./types.ts";

[gemini-code-assist]

According to the Repository Style Guide (Rule 9), changing production code in 'open-sse/' requires including corresponding tests. Please add unit tests for the newly extracted Responses lifecycle utility functions in the 'tests/' directory.

References

1. Always include tests when changing production code (src/, open-sse/, electron/, bin/).

[diegosouzapw]

Thanks, @oyi77 🙏. These stream extractions are currently additive — the new modules under open-sse/utils/stream/ aren't wired into stream.ts yet, so they don't change runtime behavior on their own. Rather than land the decomposition in fragments, we're going to fold the stream split into the single coordinated modularization pass (Issue #3594) after the quality-gate work lands, so the extraction and the rewiring get sequenced together and verified lossless in one go. Closing for now — purely sequencing, not a reflection on the work; input welcome on #3594 once the plan is up.