fix(test): build and format the teacher call comparison tests

[FeathBow]

Why

The comparison tests for teacher calls did not build, so the core test suite on main failed to compile:

• test/Comparisons.hs imported Invar.Learn.Request, which the library does not expose;
• a local binding named retried shadowed the test of the same name, which the warnings policy rejects;
• teacherSample was not in the project's Fourmolu format.

What

• The test checks that admission keeps a changed teacher call through Report.request, the value of the report's checked request, instead of the hidden request module. The library's exposed modules do not change.
• The local binding is renamed to renumbered.
• teacherSample is formatted with Fourmolu.

Validation

• All six comparison tests pass, including both teacher call tests.
• The core suite, type fixtures, Fourmolu, HLint, confidence bounds, actionlint, cabal check, sdist, and the shared, Hugging Face and MLX worker suites passed.