Add CPU-instruction budget guard around resolve_market and distribute_payouts hot path

[greatest0fallt1me]

Description

resolve_market and distribute_payouts iterate over per-user stakes and emit several events. As markets grow we risk exceeding Soroban's per-transaction CPU-instruction budget. We need a measured budget guard that aborts gracefully with a typed error before the host runs out of resources.

Requirements and Context

• Read the current instruction budget via env.budget().cpu_instruction_cost() style calls at well-defined checkpoints
• Add a BudgetGuard helper in gas.rs that records pre/post-call cost and short-circuits with Error::OperationWouldExceedBudget if remaining < configured threshold
• Wire the guard into MarketResolutionManager::resolve_market and the distribute_payouts loop in lib.rs
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b feat/cpu-instruction-budget-guard

2. Implement changes
   • contracts/predictify-hybrid/src/gas.rs
   • contracts/predictify-hybrid/src/resolution.rs
   • contracts/predictify-hybrid/src/lib.rs (call sites)
   • contracts/predictify-hybrid/src/err.rs (new OperationWouldExceedBudget variant)
3. Test and commit
   • cargo test -p predictify-hybrid budget_guard -- --nocapture
   • Cover edge cases: tiny budget, huge winner set, single winner
   • Include test output and notes in the PR

Example commit message

feat: enforce per-transaction CPU-instruction budget guard in resolution path

Acceptance Criteria

• BudgetGuard documented with /// rustdoc and used at >= 3 hot-path call sites
• New error variant emitted via events::ErrorLoggedEvent for client visibility
• Unit test reproduces an abort with a synthetic low budget
• No unwrap() on Result from budget queries

Guidelines

• Validate auth and storage TTL assumptions remain intact when aborting mid-payout
• Minimum 95% coverage of new branches
• Clear documentation and inline comments
• Timeframe: 96 hours

[annacodervibe]

@annacodervibe has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue. I have experience with Rust and Soroban smart contract development. I will follow the acceptance criteria and add tests. Excited to contribute. Kindly assign.

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

[grantfox-oss]

🦊 GrantFox — @annacodervibe has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #599)
2. Your PR will be reviewed by the Predictify-org maintainers

Good luck! Track your progress on GrantFox.

[drips-wave]

Congratulations, @annacodervibe! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @annacodervibe: 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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