Add property-based coverage for the MAX_VAULT_DURATION boundary in create_vault

[1nonlypiece]

📌 Description

tests/proptest_timestamps.rs checks ordering and the duration bound, but the
exact MAX_VAULT_DURATION boundary (end - start == MAX_VAULT_DURATION accepted
vs + 1 rejected with Error::DurationTooLong) deserves dedicated, randomized
coverage around the edge. The start_timestamp < current_time rejection path
also lacks property coverage.

Goal: extend the timestamp property tests to densely sample the duration
boundary and the past-start rejection across a randomized ledger time.

🎯 Requirements and Context

• Must be deterministic given a fixed proptest seed.
• Assert duration == MAX_VAULT_DURATION accepts and +1 rejects with
  Error::DurationTooLong.
• Assert start_timestamp < ledger.timestamp() rejects with Error::InvalidTimestamp.
• Avoid u64 overflow in generated start + duration (bounded strategies).

🛠️ Suggested Execution

1. Fork the repo and create a branch

git checkout -b feature/duration-boundary-proptests

2. Implement changes

• Tests: extend tests/proptest_timestamps.rs with boundary and past-start
  strategies, plus explicit edge vectors at exactly MAX_VAULT_DURATION.
• Docs: update the "Property Tests for Timestamp Ordering" section of
  TESTING_GUIDE.md.

3. Test and commit

• Run cargo test and regenerate coverage.
• Cover edge cases: duration exactly at max, max+1, start in the past, start ==
  now, very large bounded start_offset.

Example commit message

test: property coverage for MAX_VAULT_DURATION boundary in create_vault

✅ Guidelines

• Minimum 95% test coverage on the duration/timestamp branches.
• Clear documentation of the new property strategies.
• All tests deterministic under a fixed seed.
• Timeframe: 96 hours.

🏷️ Labels

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

💬 Community & Support

• Join the Disciplr contributor Discord to coordinate, ask questions, and get
  unblocked fast: https://discord.gg/xvNAvMJf
• Please introduce yourself before you start so we can avoid duplicate work,
  pair you with a reviewer, and merge your PR quickly.

[Muhammadcodes112]

i'll extend proptest_timestamps.rs with randomized edge coverage around the duration boundary (exact max accepted, +1 rejected) and past-start rejection. Will add explicit edge vectors, ensure deterministic execution with fixed seed, and update TESTING_GUIDE.md docs. Tests will avoid u64 overflow with bounded strategies.

Ready to start - will coordinate on Discord first.

[grantfox-oss]

🦊 GrantFox — @Muhammadcodes112 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 #230)
2. Your PR will be reviewed by the Disciplr-Org maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

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

@Muhammadcodes112's PR #245 was approved and merged by @1nonlypiece.

🏆 @Muhammadcodes112: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (153 total points). Track your full progress on GrantFox.

👏 Great work, @Muhammadcodes112! Keep contributing to Disciplr-Org.