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

[oyi77]

Part of modularization effort (Issue #3594).

Extracts Claude-specific lifecycle handling from the monolithic open-sse/utils/stream.ts into a dedicated module.

Changes:

• New file: open-sse/utils/stream/claudeLifecycle.ts (179 lines)
• Exports: SYNTHETIC_CLAUDE_EMPTY_RESPONSE_TEXT, createClaudeEmptyResponseLifecycle, getClaudeEventType, isClaudeEventPayload, updateClaudeEmptyResponseLifecycle, shouldInjectClaudeEmptyResponseBeforeCurrentEvent, shouldInjectClaudeEmptyResponseOnFlush, shouldInjectClaudeMissingFinalizersOnFlush, buildSyntheticClaudeEmptyResponseEvents, restoreClaudePassthroughToolUseName

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), responsesLifecycle, and streamCore.

[gemini-code-assist]

Code Review

This pull request introduces a new utility file open-sse/utils/stream/claudeLifecycle.ts to manage and track the lifecycle of Claude empty responses in SSE streams. The review feedback identifies unused and invalid imports (convertOpenAIToResponsesToolCall and uuidv4) at the top of the file that will cause compilation or runtime errors and should be removed.

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[gemini-code-assist]

The imports convertOpenAIToResponsesToolCall and uuidv4 are unused in this file. Additionally, convertOpenAIToResponsesToolCall is not exported by ../handlers/responseTranslator.ts, which will cause a compilation or runtime error. These unused and invalid imports should be removed.

Suggested change

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

[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.