Docs rules: no em-dash, uv/ppp/tcl examples only, pythonx-compose tone #136

Maintainer (2026-10-03): no em-dash anywhere (docs and code); guides use uv, ppp or tcl, never pip install; doc tone follows pythonx-compose's guide. Completion: AGENTS.md states the rules; a follow-up removes existing em-dashes and pip examples (after #131 lands, to avoid conflicts).