upgrade-governance: add upgrade rollback proposal type

[Emeka000]

Summary

Once an upgrade is executed there is no on-chain mechanism to propose and vote on reverting to a previous WASM hash. If a bug is discovered post-upgrade, rollback requires manually re-proposing the old hash without any rollback semantics or guards.

Proposed Change

• Add propose_rollback(signer, target_proposal_id) that creates a rollback proposal pre-populated with the WASM hash and metadata from a previously executed proposal
• Rollback proposals require the same signer threshold as standard upgrades
• Emit a UpgradeRollbackProposed { rollback_proposal_id, original_proposal_id, wasm_hash } event
• Add max_rollback_age_ledgers config — rollback to proposals older than this is blocked

Acceptance Criteria

• Rollback proposal references original proposal ID
• Rollback blocked for proposals older than max age
• Rollback follows same voting and timelock flow as regular upgrade
• Test covers: propose, vote, execute rollback cycle

[rotimitimilehinsamuel-ops]

@rotimitimilehinsamuel-ops has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I can implement the upgrade rollback proposal type so governance can safely revert to a previous WASM hash instead of manual workarounds.
I have experience with Soroban, Rust, and on-chain governance. Kindly assign this issue to me.

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

[OjoJoel1996]

@OjoJoel1996 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

1. Hello Maintainer, I've reviewed the issue and understand the requirements. I'm confident I can implement an effective solution. I'd appreciate it if you could assign this issue to me.

2. Based on the requirements, I'll implement the necessary changes to ensure the solution aligns with the design specifications and satisfies all acceptance criteria.

3. Hello, I've carefully reviewed the issue requirements and understand the expected outcome. I'm confident I can deliver a solution that meets the acceptance criteria. Kindly assign this issue to me.

4. Hi Maintainer, I'd be happy to work on this issue. I have experience with similar tasks and can begin implementation right away.

5. Hello, I'm interested in contributing to this issue and would appreciate the opportunity to work on it. Please consider assigning it to me. Thank you!

6. Hi, I've carefully gone through the issue details and am confident I can deliver a clean, efficient, and well-tested solution.

7. Hello Maintainer, I'd like to take ownership of this issue and submit a high-quality pull request that fully addresses the requirements.

8. I've thoroughly reviewed the requirements and will implement a clean, maintainable solution that meets the project's standards and acceptance criteria.

9. Hello, This issue aligns well with my experience and technical skills. I'm confident I can resolve it effectively. Kindly assign it to me.

10. Hi Maintainer, I'm interested in contributing to this task. I can provide a clean implementation, follow best practices, and deliver the solution promptly.

11. Hello, I've carefully reviewed the issue description and understand the expected outcome. I'd be glad to work on this task and would appreciate being assigned to it.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @OjoJoel1996 to this issue.

[Bug00Joe]

@Bug00Joe has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi! I'd like to take this issue on.

I have experience with Rust/Soroban contract governance and upgrade mechanisms, so this fits well.

Plan: add propose_rollback(signer, target_proposal_id), which looks up a previously executed proposal and creates a new rollback proposal pre-populated with its WASM hash and metadata. I'll enforce the same signer threshold as standard upgrades, and add a max_rollback_age_ledgers config that blocks rollback proposals referencing proposals older than that window. The rollback will follow the existing voting and timelock flow rather than introducing a separate path, and I'll emit UpgradeRollbackProposed { rollback_proposal_id, original_proposal_id, wasm_hash } on creation. Tests will cover the full propose → vote → execute rollback cycle, plus the max-age rejection case.

Would appreciate being assigned this one. Thanks!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Bug00Joe to this issue.

[yusufmuhammadayodeji-netizen]

@yusufmuhammadayodeji-netizen has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello, I’ve gone through the requirements and I’m confident I can implement a proper solution that matches the acceptance criteria. Kindly assign this issue to me.

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

[a34722429-alt]

@a34722429-alt has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

i would like to work on this issue please

ℹ️ Repo Maintainers: To accept this application, review their application or assign @a34722429-alt to this issue.

[drips-wave]

Congratulations, @yusufmuhammadayodeji-netizen! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

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