Plectis v0.1.0

Plectis v0.1.0 binds the public clone/run path to CI-backed onboarding evidence.\n\nValidation:\n- CI run 28187654563 passed on Python 3.11, 3.12, and 3.13.\n- The user-smoke/timing job passed and uploaded the onboarding benchmark artifact.\n- Fresh public clone benchmark for b76fa19: clone 2.452s, bootstrap 0.878s, smoke 2.899s, install 14.815s, installed tour 1.257s, total 22.591s.\n\nSupported first-user path: Python 3.11+ with a POSIX shell, ./bootstrap.sh, then make smoke. Windows users should use WSL until native Windows CI exists.