fix(types): return jest from setSystemTime

[ShiroKSH]

What changed

• Declare jest.setSystemTime() as returning the jest object, matching the runtime.
• Add an exact-type regression assertion to the bun-types fixture.

Why

The native host function returns its receiver, but the declaration reported void. This prevented typed fluent usage even though it already works at runtime.

Verification

• TypeScript 6 compile check without DOM types
• TypeScript 6 compile check with DOM types
• Current-main Bun runtime check: jest.setSystemTime() === jest
• Regression assertion fails with the old declaration and passes with this change

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between c1076ce and 93adef0.

📒 Files selected for processing (2)

• packages/bun-types/test.d.ts
• test/integration/bun-types/fixture/mocks.ts

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Walkthrough

Changes

setSystemTime type contract

Layer / File(s)	Summary
Update declaration and validate return type packages/bun-types/test.d.ts, test/integration/bun-types/fixture/mocks.ts	jest.setSystemTime now returns typeof jest, and a fixture assertion validates the updated type.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main change to setSystemTime's return type.
Description check	✅ Passed	The PR explains the change, motivation, and verification, covering the template's required information.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[ShiroKSH]

@alii - Buildkite has been pending since July 10, and CodeRabbit reported no actionable issues. Could you approve or restart the CI run, or route this to the right reviewer? I can make any requested changes. Thanks!

[ShiroKSH]

Hi maintainers, this PR has been open for over two weeks. When you have a moment, I would appreciate a review. Thank you.

[robobun]

Triage note: this is not on main yet (checked at f426a8e), the branch still merges cleanly, and bun test test/integration/bun-types/bun-types.test.ts passes with it applied. #36505, which had copied this fix into a batch, has been cut down so it no longer overlaps; this PR is the one to land for it.

One heads up: #32333, #32335, #32455 and #33923 all append to the end of test/integration/bun-types/fixture/mocks.ts, so whichever of them lands first will put the other three into a trivial conflict (keep both sides). A quick rebase at that point should be all that is needed. #32455 also inserts now() directly below the setSystemTime line this PR changes in test.d.ts, so that one conflicts the same way.

Thanks for the fix and for the patience.