[Refactor] Roll out stream helpers to LiteLLM and Z.ai specs

[zoomote]

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

What changed

• Migrated lite-llm.spec.ts to the shared stream helpers, replacing all inline async-iterator mock streams with asyncStreamFrom and all pure result/drain loops with collectStream.
• Migrated zai.spec.ts to the same helpers, replacing custom [Symbol.asyncIterator] next-chain mocks with asyncStreamFrom.
• Switched describe-scoped LiteLLM mock streams to fresh makeMockStream() factories so each test gets an unconsumed generator.
• Removed the unused collectStream import from zai.spec.ts.
• Left existing ESLint suppressions counts unchanged after verification.

Why this change was made

This is the more ambitious continuation of the approved test-utils rollout: two high-count provider specs migrated in one PR while keeping single-chunk .next() assertions inline where they are the point of the test.

Impact

No user-facing behavior change. Eighty-one targeted provider 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
• OpenAI spec stream-helper migration: [Refactor] Roll out stream helpers to OpenAI spec #1093
• Anthropic Vertex stream-helper migration: [Refactor] Roll out stream helpers to Anthropic Vertex spec #1094

[zoomote]

No code issues found. See task

• src/api/providers/__tests__/lite-llm.spec.ts:1055 and src/api/providers/__tests__/lite-llm.spec.ts:1188 — The describe-scope const mockStream = asyncStreamFrom([...]) created a single-use AsyncGenerator shared across every test in the describe block. Fixed in 838d3fb: both describes now use a makeMockStream() factory called fresh inside each test's mockCreate.mockReturnValue(...).
• src/api/providers/__tests__/zai.spec.ts:17 — collectStream was imported but never used. Fixed in 838d3fb: import reduced to asyncStreamFrom only.

_{Reviewed 838d3fb}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[zoomote]

Addressed both outstanding review findings.

• LiteLLM describe-scoped mock streams are now fresh makeMockStream() factories called inside each test, so tests no longer share a single-use generator.
• Removed the unused collectStream import from zai.spec.ts.
• Commit: 838d3fba585ed84909df39794da2f4f5519b24a8
• Validation: targeted LiteLLM + Z.ai specs, check-types, and lint passed before push; PR metadata refreshed.
• Thread state: no inline review threads existed for these findings; the fixes are reflected in the updated PR body.