Build a small, self-contained tool from an empty tree: it reads a file of append-only record entries, checks that each entry's hash links correctly to the one before it, reports the first break clearly, and exits non-zero on any inconsistency. Depend on nothing outside the language's standard library — no packages are available.

Write the layout, the build configuration, the tests, and the check command the verifier should run, and make sure that check command actually examines the code rather than passing on an empty suite.