{# THE shell. One nav, one head, one skip link, one
. Derived once from docs/design/040/_build.py::nav() + head() + page(), which exist in the mockup set for exactly this reason: so the frame stays byte-identical across screens and the claim is checkable rather than promised. Rule 1 of the design system is "one nav component; it rotates axis at 768 px; it never forks" — the rotation is pure CSS (app.css, @media 768px), so there is one markup here and there will never be a second. The LOOK is the design of record (webview/static/css, loaded below); the mockups are its schema. A screen extends this and fills {% block body %}. It does not restate the frame, and it must not introduce a second