[Refactor] Batch roll out stream helpers to OpenAI-family specs

[zoomote]

Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Batched the shared stream-helper rollout across four OpenAI-family provider specs: openrouter, openai-codex, openai-native-tools, and openai-codex-native-tool-calls.
• Replaced pure async-iterator mock streams with asyncStreamFrom and pure collect/drain loops with collectStream, including local helper reimplementations where those helpers were just duplicating the shared pattern.
• Left side-effect generator loops inline where the loop itself drives NativeToolCallParser state.
• Reduced ESLint suppression counts only where the refactor removed explicit-any violations.

Why this change was made

This is the more ambitious continuation of the approved test-utils rollout: a cohesive multi-file batch instead of another single-spec migration, with the same rule that helpers only remove mechanical stream setup and collection.

Impact

No user-facing behavior change. Four provider specs now share the same stream-helper idiom, targeted batch tests passed, src lint/typecheck passed, and the full Zoo-Code test suite passed.

Related PRs

• Async-stream test-utils pilot: [Refactor] Pilot shared stream test utilities #1086
• Requesty stream-helper rollout: [Refactor] Roll out stream helpers to Requesty spec #1089
• Unbound stream-helper rollout: [Refactor] Roll out stream helpers to Unbound spec #1090

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1 issue outstanding. See task

• src/api/providers/__tests__/openai-codex-native-tool-calls.spec.ts:47 — The refactor dropped the comment noting that the response.function_call_arguments.delta fixture intentionally omits call_id + name to simulate tool-call-only streams. Without it, a future reader may "fix" the fixture and silently weaken the test; consider restoring the note.

_{Reviewed 1877e2b}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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