…ng (codeceptjs#5412)

The sorting of test files in loadTests() (added in codeceptjs#5386) broke the
--by suite parallelization. When files were sorted before worker
distribution, all workers could receive the same tests instead of
different suites being distributed to different workers.

Fix: Move testFiles.sort() from loadTests() to run(). This ensures:
- Worker distribution uses original (unsorted) file order for consistent
  distribution across workers
- Test execution still uses alphabetical order (sorted in run())

Added unit test to verify files are not sorted after loadTests().

Fixes codeceptjs#5412

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>