Add regression test for buyback KeysBoughtBack event containing correct new_supply value

[Chucks1093]

Summary

The KeysBoughtBack event must include the updated total supply after the buyback completes. A regression test should confirm the new_supply field equals the pre-buyback supply minus the buyback amount.

Scope

• Record total supply before a buyback
• Execute a buyback for a known amount
• Capture the emitted KeysBoughtBack event
• Assert new_supply equals pre-buyback supply minus the buyback amount

Acceptance Criteria

• new_supply field equals pre-buyback supply minus buyback amount
• Event field is present and not zero when supply remains after buyback
• Full buyback of all supply results in new_supply of zero

ETA: 12 hours

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Coordinate on Telegram

[harystyleseze]

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[gloskull]

Hi, I’d love to work on this issue. I have 4 years of experience across backend, frontend, full-stack, and smart contract development. I understand the task clearly and can deliver a clean, efficient, well-tested solution on time, with strong focus on code quality and maintainability. My PR will be submitted in under 10 hours.

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