Add test coverage for harvest()

[devsimze]

Problem

harvest() (Issue #465, merged via PR #491) has zero test coverage — there is no test_harvest.rs and no other test file references harvest.

Scope

• neurowealth-vault/contracts/vault/src/lib.rs (harvest)
• New neurowealth-vault/contracts/vault/src/tests/test_harvest.rs

Acceptance criteria

• Success path: harvest withdraws and re-supplies to CurrentProtocol, emits HarvestEvent with correct protocol/amount_harvested.
• Rejects when vault is paused.
• Rejects when caller is not the agent.
• Rejects negative min_out.
• Rejects when CurrentProtocol is none (UnsupportedProtocol).
• Rejects when called before the rebalance cooldown elapses.

[Muyideen-js]

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

Hi, I can fix this

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[uche102]

@uche102 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer please i would like to work on this

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[p4uld4vid016-code]

@p4uld4vid016-code has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer, i would like to work on this issue

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[onakijames-droid]

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

Hi maintainer... I'll work on this issue and submit a PR for it ASAP

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[JACTech001]

@JACTech001 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi! I would like to work on this issue. I have relevant experience with this stack and can deliver a clean solution that meets all the acceptance criteria. Ready to start once assigned!

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[drips-wave]

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

🧑‍💻 @onakijames-droid: 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.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@onakijames-droid's PR #683 was approved and merged by @Abidoyesimze.

🏆 @onakijames-droid: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (201 total points). Track your full progress on GrantFox.

👏 Great work, @onakijames-droid! Keep contributing to Neurowealth.