[Refactor] Modernize sleep function using node:timers/promises

[gonzaloriestra]

WHY are these changes introduced?

The sleep function in packages/cli-kit/src/public/node/system.ts was using an outdated manual Promise wrapper around setTimeout. Modernizing it to use node:timers/promises makes the code cleaner and leverages native Node.js capabilities.

WHAT is this pull request doing?

• Imports setTimeout from timers/promises in packages/cli-kit/src/public/node/system.ts.
• Refactors sleep to use await setTimeout(...).
• Adds a unit test for sleep in packages/cli-kit/src/public/node/system.test.ts.

How to test your changes?

CI

Post-release steps

None.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

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PR created automatically by Jules for task 6335028973932666746 started by @gonzaloriestra

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