Plan step 25 (navigation Missing): M3's "alignment: top or center; on tablets
prefer center alignment for reach" had no implementation — the rail was
top-aligned only. `<x-navigation-rail align="center">` centres the destinations
between the header and the footer, which stay at their ends because M3 keeps the
menu icon and the FAB top-aligned. `safe center` gives the top back the moment
there are more destinations than fit, where centring would push the first one
out of reach above the scroller.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9