Ensure CI pipeline passes

[dgenio]

Summary

Verify and fix the full CI pipeline.

Pipeline

ruff format src/ tests/ examples/
ruff check src/ tests/ examples/
mypy src/
python -m pytest -q --tb=short
python examples/basic_cli.py
python examples/billing_demo.py
python examples/http_driver_demo.py

GitHub Actions

Verify .github/workflows/ci.yml runs on Python 3.10, 3.11, 3.12 with:

• ruff (format check + lint)
• mypy
• pytest

Acceptance criteria

• make ci passes locally
• All 3 examples exit 0
• No mypy errors
• No ruff errors
• GitHub Actions workflow file is valid