Remove duplicate TestCase (sibling of verapdf dedup)

[jbagsik]

Context

Confirmed sibling of the veraPDF duplicate-TestCase defect: kosit-validator also ships two identical files — src/Tests/TestCase.php and tests/TestCase.php — both declaring Moox\KositValidator\Tests\TestCase (verified diff-clean). The veraPDF smell was copied from here.

What to build

kosit-validator has exactly one Moox\KositValidator\Tests\TestCase, resolved through composer autoloading, with no duplicate file and no runtime autoloader shim.

Acceptance criteria

• Only one TestCase file remains (canonical location per package convention; the duplicate is deleted).
• composer.json autoload-dev maps the Tests\ namespace to the kept location; the in-file autoloader shim is removed.
• Pest.php still resolves TestCase; the full package suite runs green.
• SonarQube no longer reports duplication for the removed file.

Blocked by

None — can start immediately.

[jbagsik]

Additional acceptance criteria — Codacy findings on the TestCase file (fold in here):

• The kept TestCase file contains a single class in its own file (Codacy: "each class must be in a file by itself") — resolve the conditional double-class declaration (Orchestra vs ApplicationTestCase) so only one class is declared per file.
• The file declares symbols with no side effects (Codacy: side-effect + symbol in one file) — removing the in-file autoloader shim already covers this; confirm no other top-level side effects remain.