coco-cashu adapter contract tests

This package exports reusable test helpers that verify whether a storage adapter
conforms to the Repositories contract from coco-cashu-core.

Usage

Install the package as a devDependency inside an adapter package and wire the
contract suite into your test runner:

``ts
import { describe, it, expect } from 'bun:test';
import { runRepositoryTransactionContract } from 'coco-cashu-adapter-tests';
import { MyAdapterRepositories } from './src';

runRepositoryTransactionContract(
{
createRepositories: async () => {
const repositories = new MyAdapterRepositories(options);
await repositories.init();
return {
repositories,
dispose: async () => repositories.close?.(),
};
},
},
{ describe, it, expect },
);
`

The factory is responsible for providing a fresh, isolated repositories
instance for every test and for cleaning up via dispose()`.