Plan step 25 (navigation Missing): M3's "Expanded behavior | Hide when
collapsed" was only implicit below `medium` in the adaptive rail.
`<x-navigation-rail hide-when-collapsed>` (collapsible and adaptive rails) takes
the rail out of the layout when it is collapsed; `$store.rail.show()` from an
app-bar menu button brings it back expanded over a scrim, sliding in, and its
own menu button docks it again. It does not reach the bands where the window,
not the visitor, collapses a rail (below `medium` for collapsible, `medium` for
adaptive), since M3's collapsed rail may never hide. Every `rail-collapsed`
branch now stops while the rail is open. `<x-app-shell hide-rail-when-collapsed>`
exposes it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9
