Add boundary tests for the claim logic

[mikewheeleer]

Boundary-test claim

Description

claim's boundaries aren't fully tested. This issue adds cases.

Requirements and context

• Repository scope: Agentpay-Org/Agentpay-contracts only.
• Add tests for claim at min, max, zero, and over-limit inputs asserting typed errors where expected.
• Keep runs bounded.
• Note any unguarded boundary.

Suggested execution

• Fork the repo and create a branch
• git checkout -b test/claim-91-boundary
• Implement changes
  • Write code in: the relevant module.
  • Write comprehensive tests in: cover the new behaviour and edge cases.
• Test and commit

Test and commit

• Run cargo fmt, cargo clippy --all-targets -- -D warnings, and cargo test.
• Cover edge cases: min, max, zero, over-limit.
• Include the full test output in the PR description.

Example commit message

test(claim): add boundary tests

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the AgentPay community on Discord: https://discord.gg/eXvRKkgcv
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — a 5-star rating is much appreciated.