Add grace_period enforcement to commitment_core::check_violations

[1nonlypiece]

📌 Description

CommitmentRules in contracts/commitment_core/src/lib.rs carries a
grace_period_days field, but check_violations (line ~983) and
get_violation_details (line ~1008) appear to flag duration/loss violations without
honouring that grace window. A provider in a temporary drawdown during the declared
grace period can therefore be marked violated prematurely.

This issue makes grace_period_days a real invariant in the violation logic.

🎯 Requirements and Context

• During the grace window, loss-limit and expiry checks must be relaxed per the documented grace_period_days semantics.
• Time math must use shared_utils::TimeUtils with checked arithmetic (no expires_at + grace overflow).
• Must not weaken violation detection outside the grace window — preserve test_check_violations_* snapshots.
• get_violation_details return tuple semantics must stay backward-compatible.

🛠️ Suggested Execution

1. Fork the repo and create a branch

git checkout -b feature/grace-period-enforcement

2. Implement changes

• Update check_violations and get_violation_details in contracts/commitment_core/src/lib.rs to factor in grace_period_days.
• Add /// docs describing grace semantics; update docs/commitment_core/SEMANTICS.md.

3. Test and commit

• Extend contracts/commitment_core/src/tests.rs.
• Run: cargo test --target wasm32v1-none --release
• Edge cases: violation inside grace, violation after grace, grace=0, grace causing expiry overflow.

Example commit message

feat: enforce grace_period_days in commitment violation checks

✅ Guidelines

• Minimum 95% test coverage on the new/changed lines.
• Document grace semantics clearly.
• Timeframe: 96 hours.

🏷️ Labels

type-feature · area-contracts · MAYBE REWARDED · GRANTFOX OSS · OFFICIAL CAMPAIGN

💬 Community & Support

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[dangelo352]

I can take this one. I will enforce grace_period_days in commitment_core violation checks with checked time math, preserve existing tuple semantics, add inside/after-grace and overflow coverage, and update the commitment semantics docs.