Feat/expand payload validation tests

[vicajohn]

closes #606

Overview

Related Issue

Closes #

Changes

Verification

# e.g.
cd dashboard && npm test
cd listener && npm run typecheck && npm test
cd contract/contracts/hello-world && cargo test

How to Test

Checklist

• Branch is up to date with main
• Tests added/updated and all pass locally
• cargo fmt --all run (if Rust changes)
• npm run lint passes (if TypeScript changes)
• Documentation updated if behavior changed