43539c70 - does the project's current in-progress sprint item call for test/coverage work?

Powers the PostToolUse test-tamper guard's exemption. The guard flags any test-file edit as a possible "make a failing test pass by editing the test" tamper - UNLESS the item being worked explicitly asks for new/updated tests (legitimate feature work adds tests). Returns {"test_coverage_expected": bool}. Distinct /sprint/ path, mirroring /sprint/pending_count, so there is no collision with /sprint-items.