The home index and every page breadcrumb link a project root
`<a href="/<slug>/">`, but the router declared only `/`, `/assets/theme.css`,
and the `/{slug}/{*page}` catch-all (which requires a concrete page segment),
so every project-root link 404'd. Add a `/{slug}/` route and a project_index
handler that renders a landing page listing the project's sections and pages
(unknown slug -> 404); the index and breadcrumb root links are now live.
RED-first via the debug skill: tests/e2e.rs
`project_root_resolves_to_landing_with_section_nav` (a GET to /aura/ asserting
200 + the section/page nav) failed 404 before the fix, passes after.
cargo test green (42); clippy clean.
Brummel
d5a2dce7ef