add slashing adversarial scenarios and fix hardhat setup

[Cedarich]

• Summary

• Add adversarial and edge‑case tests for TruthBountyWeighted and VerifierSlashing.

• Fix TypeScript diagnostics in test files by loosening contract typings and using proper Hardhat chai helpers.

• Align Hardhat/toolbox configuration so the test suite runs cleanly.

• Changes

• test/TruthBountyWeighted.test.ts

  • Add tests for loser slashing on withdrawal, double‑withdraw prevention, locked‑stake withdrawal, and non‑voter withdrawal.
  • Fix event assertions to use anyValue from @nomicfoundation/hardhat-chai-matchers/withArgs .
  • Relax contract types to avoid BaseContract method errors and fix bigint arithmetic typings.

• test/VerifierSlashing.test.ts

  • Add adversarial scenarios: multiple partial slashes over time, cooldown enforced across multiple settlement addresses, slashing + withdraw interaction, and batch slashing with a zero‑stake verifier.
  • Relax contract instance typings to avoid BaseContract method errors and remove unused variables.

• package.json

  • Set devDependencies to hardhat@^2.28.0 and @nomicfoundation/hardhat-toolbox@^6.1.0 .
  • Set "type": "commonjs" to resolve Hardhat HH19 ESM config issues.

• Testing

• npm.cmd run test

  • All Hardhat tests pas

close issue #32