Add a reusable fullwidth layout (layouts/fullwidth.njk) for rich HTML
content that needs the full container width without sidebar or prose
constraints. Add the interactive architecture explorer as a static
asset served via passthrough copy at /interactive/architecture.html.
- layouts/fullwidth.njk: site header + footer only, no sidebar
- interactive/architecture.html: tabbed architecture guide
- eleventy.config.js: passthrough copy for interactive/ directory
