M3 asks the rail to animate its FAB into an extended FAB as it expands; the
documented pattern was two FABs swapped by `display`, so the collapsed one
appeared at once while the rail's width was still springing. The header now takes
one <x-fab label icon> whose label springs open and shut on the rail's own
spring — and names it at both widths, where the collapsed FAB had needed a
tooltip to have a name at all.
M3 also lists two container treatments as optional that the library had neither
of: `divider` draws the vertical divider on the page's edge, which is its own
answer to a page scrolling under a fixed rail, and `fill="false"` drops the
container colour. Neither reaches a rail open over a scrim. And a `collapsible`
rail, whose width is the visitor's choice rather than the window's, is held to
the collapsed 96px below `medium`, where M3 asks for a navigation bar instead.
Plan: docs/plans/material-3-alignment.md, step 21 (navigation N-22, N-23, N-24).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9
M3 Expressive's flexible navigation bar, the collapsed, expanded and
modal navigation rail with its state applied before the first paint,
and an adaptive app shell composing them. The head script now restores
the theme and rail attributes that wire:navigate strips from <html>.
Completes Phase 8.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V9NnLxnPp8vaaurb3Z1MFy
