Add boundary tests for Drand round time helpers

[karagozemin]

Goal\nCover genesis and round-boundary behavior in the Drand time helpers.\n\n## Acceptance criteria\n- Test before genesis, genesis, and adjacent round boundaries.\n- Test round/time inverse behavior.\n- Keep tests fully offline.\n\n## Wave complexity (maintainer)\nHigh - 200 points

[abdulwahabmonilola-ctrl]

@abdulwahabmonilola-ctrl has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer, I’m interested in working on this issue. I have experience with similar tasks and can begin immediately.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @abdulwahabmonilola-ctrl to this issue.

[francisprecious061]

@francisprecious061 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer, i'd love to fix this... Assign me.

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[veemakama]

@veemakama has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi, i would love to work on this.

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[merciiiqode]

@merciiiqode has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

i want to work on this

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[akinerin]

@akinerin has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would love to work on this issue, please assign it to me

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[drips-wave]

Congratulations, @akinerin! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @akinerin: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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