fix: remove em dashes from README prose

seo: improve README opening, hook line, and section headers

feat: add Claude Code skill interface and update README

ci: skip integration tests gracefully when API key secret is absent

Fix mypy errors: add BaseDetector inheritance to detectors, type dict in CLI

Apply ruff formatting to pass CI format check

Add GitHub Actions CI workflow

Temporarily exclude .github/workflows from push (token lacks workflow scope)

Initial commit: humanizer-workbench CLI with multi-stage AI text rewriting pipeline