Split the monolithic `src/csv-loader/loader.test.ts` into multiple
specialized test files to improve maintainability and readability:
- `parseCsv-basic.test.ts`: Primitive types, arrays, and tuples
- `parseCsv-caching.test.ts`: Table caching logic
- `parseCsv-circular.test.ts`: Circular reference detection
- `parseCsv-combinators.test.ts`: References in unions and tuples
- `parseCsv-noResolveRefs.
