Add GitHub Actions CI workflow for testing (#4)

- Add test.yml workflow that runs on PRs and main branch pushes
- Test on Python 3.10 and 3.11 across ubuntu-latest and macos-latest
- Use uv for fast dependency management
- Run pytest and ruff linter/formatter checks
- Linting checks are non-blocking to allow iteration on code quality
- Fix multiple ruff linting issues (unused imports, f-string placeholders, ambiguous variable names)

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: abrichr

src/openadapt_viewer/cli.py

@@ -285,7 +285,6 @@ def run_benchmark_command(args):
         print("Generating benchmark viewer with REAL nightshift recording data...")
     else:
         print(f"Generating benchmark viewer from: {args.data}")
-
     output_path = generate_benchmark_html(
         data_path=args.data,
         output_path=args.output,