Add regression tests for concurrent open/execute races on the same settlement id in settlementRepository

[Jagadeeshftw]

📌 Description

SettlementRepository in src/repositories/settlementRepository.ts tracks nextId, reserved, and consumed liquidity in memory. Node's single-threaded event loop makes true races unlikely, but interleaved async handlers (e.g. two execute/cancel calls for the same id issued back-to-back) are not covered by settlementRepository.test.ts, and a bug here could double-release or double-consume reserved liquidity.

🧩 Requirements and context

• Add tests that fire execute/cancel for the same settlement id from two concurrent promise chains and assert only one succeeds, the other gets a defined error (already-executed/already-cancelled).
• Assert reserved liquidity is released exactly once regardless of call ordering.
• Document the repository's concurrency assumptions (single in-process instance, no external locking) in a code comment.

🛠️ Suggested execution

• Extend src/repositories/settlementRepository.test.ts with interleaved-call scenarios using Promise.all.
• If a real double-consume/double-release bug surfaces, fix it in settlementRepository.ts and add a targeted regression test.
• Cross-check src/services/settlementService.ts for any additional guard it relies on the repository to provide.

✅ Acceptance criteria

• Concurrent execute/cancel calls on one settlement never double-mutate reserved/consumed state.
• Losing call in a race gets a clear, tested error.
• Concurrency assumptions documented in code.

🔒 Security notes

Prevents a liquidity-accounting bug (double release) that could let more be withdrawn than was ever reserved.

📋 Guidelines

• Minimum 95% test coverage
• Clear documentation
• Timeframe: 96 hours

[GBOYEE]

Hi \u2014 I can take this on (Add regression tests for concurrent open/execute races on the same ...). I'll build the UI per the acceptance criteria. Happy to submit a PR for this once the bot assigns it.

[Jagadeeshftw]

@GBOYEE thanks for the interest — you're currently at the 6 open-issue assignment cap for this repo, so I can't assign this one right now (backfill automation). Please finish or release one of your existing assigned issues, then request this one again and it'll be picked up.

[grantfox-oss]

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Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #77)
2. Your PR will be reviewed by the AnchorNet-Org maintainers

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