Add tests workflow

[EduardoPach]

What does this PR do?

This PR adds CI infrastructure for automated testing and removes the Docker dependency from WDER (Word Diarization Error Rate) tests by migrating to HuggingFace-hosted test fixtures and hardcoded expected values for simple inputs.

Changes

CI Infrastructure

• Added GitHub Actions workflow (.github/workflows/tests.yml) with two jobs:
  • Check Format: Runs Ruff linter and formatter checks
  • Run Tests: Sets up uv and executes test suite via make test
• Workflow triggers on pull requests to main branch

Test Improvements

• Removed Docker dependency for WDER reference implementation
  • Deleted Dockerfile and wder_reference.py that wrapped Google's diarizationlm library
  • Tests now use precomputed expected values from HuggingFace fixtures
• Added real-world test cases:
  • test_wder_real_more_hyp_speakers: Tests with more hypothesis speakers than reference
  • test_wder_real_fewer_hyp_speakers: Tests with fewer hypothesis speakers than reference
• Simplified test approach: Compare against expected values instead of running reference implementation
• Test fixtures hosted at argmaxinc/test-fixtures on HuggingFace

Code Formatting

• Applied Ruff formatting across multiple files
• Cleaned up import ordering and line length issues
• Reformatted long lines in whisperkitpro_engine.py, transcription_oss_whisper.py, and transcription_whisperkitpro.py

[dbrkn]

lgtm