Formatting, hooks & CI — make the standard the default

Scanner path: commands below assume tools/cc-scan.py / tools/arch-scan.py are in the repo. If they are not, the same scanners may be on PATH as cc-scan / arch-scan (identical flags) — see INSTALL.md §1b. If neither exists, ask for the report instead of guessing numbers.

A rule nobody enforces is a suggestion. This skill is about moving decisions out of code review and into tooling, so review time goes to design instead of commas.

0. Division of labour (exactly one owner per decision)