[Refactor] Roll out stream helpers to Unbound spec

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

What changed

• Refactored src/api/providers/__tests__/unbound.spec.ts to replace inline async-iterator mock streams with asyncStreamFrom and pure stream collection/drain loops with collectStream.
• Reduced the unbound.spec.ts ESLint suppressions count after removing the obsolete chunks: any[] declarations.

Why this change was made

This continues the approved test-utils rollout with another provider spec, using the same narrow rule: extract mechanical stream setup and collection, while leaving assertions and request-shape checks explicit.

Impact

No user-facing behavior change. The Unbound spec follows the shared stream-helper pattern, and the targeted spec, src lint/typecheck, and full Zoo-Code test suite passed.

Related PRs

• Async-stream test-utils pilot: [Refactor] Pilot shared stream test utilities #1086
• Webview test query client helper follow-up: [Refactor] Reuse webview test query client helper #1088
• Requesty stream-helper rollout: [Refactor] Roll out stream helpers to Requesty spec #1089

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No code issues found. See task

_{Reviewed 52450f5}

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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