Adds the pages the rebuilt navigation is organised around, and moves the sidebar
onto that structure. Every entry points at a file that exists after this commit;
nothing is rewritten or removed yet, and no redirect is claimed yet.
- Studio (13 pages) — the editor had no section of its own
- One guide per creation workflow, matching the shipped agent skills
- Section hubs: Concepts, Catalog, Developers, Deploy, Workflows, Help,
Go further, Product updates, 30 Days of HyperFrames
Pages a later commit retires drop out of the sidebar here but still exist and
still resolve, so the site stays navigable at this commit.
Incidentally fixes a link to /concepts from the Lambda migration guide that is
broken on main today — the destination did not exist.
