Let a rail hide when collapsed instead of narrowing

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

resources/boost/skills/livewire-material-development/SKILL.md

@@ -718,7 +718,7 @@ A visitor who has pressed the menu button keeps that choice in both standard ban
 ```
 
 - `destinations`: `title`, `icon`, `url`; optional `active` (default: the URL is the page's, also during a Livewire update request), `badge` (`true` for a dot, or a count), `badgeLabel` (what a screen reader hears for the badge: "3 unread"), `section` (a heading in the rail, shown only while it is expanded; consecutive destinations with the same section are grouped), `bar` (default `true`; `false` keeps it out of the bottom bar — M3 wants three to five there), `navigate` (`false` for a full page load instead of `wire:navigate`).
-- Slots, each rendered once: `banner` (a bar across the whole window, above the rail and the page), `brand` (beside the rail's menu button, expanded only), `rail-header` (a FAB), `rail-footer` (pinned to the foot of the rail), `actions` (a row of icon buttons at the very foot, stacked when collapsed), `top` (the page's own bar, above the page and beside the rail), and the page. `label` names the landmarks ("Main"); `rail-width` is the expanded width (`16rem`); `tall-bar` picks M3's 80px navigation bar over the 64px one; `hide-bar-on-scroll` lets the bar leave the window while the page scrolls down.
+- Slots, each rendered once: `banner` (a bar across the whole window, above the rail and the page), `brand` (beside the rail's menu button, expanded only), `rail-header` (a FAB), `rail-footer` (pinned to the foot of the rail), `actions` (a row of icon buttons at the very foot, stacked when collapsed), `top` (the page's own bar, above the page and beside the rail), and the page. `label` names the landmarks ("Main"); `rail-width` is the expanded width (`16rem`); `tall-bar` picks M3's 80px navigation bar over the 64px one; `hide-bar-on-scroll` lets the bar leave the window while the page scrolls down; `hide-rail-when-collapsed` takes the rail out of the layout from `expanded` when its menu button collapses it, instead of narrowing it to 96px — the only way back is `$store.rail.show()`, so the app bar then needs a menu button at every width.
 - `banner` or `top`: M3's scaffold is bars, then rails, then panes. An application-wide bar — one search, one account menu, the same on every page — goes in `banner` and the rail starts under it; a bar that titles the page goes in `top`, beside the rail. Never both. A banner that pins itself to the top of the window says how tall it is (`style="--material-banner: 4rem"` on `<x-app-shell>`), so the rail sticks under it instead of behind it.
 - The rail is one element at every width: what is in it is also what a phone sees in the modal rail. On a compact window nothing opens it but `$store.rail.show()`, so a page whose destinations are not all in the bar needs a menu button in its app bar (hidden from `medium`).
 - `--material-margin` is M3's window margin (16px compact, 24px from `medium`) and the content region already carries it, so a page inside the shell writes no gutters of its own; something that must reach the window's edges opts out with `-mx-(--material-margin)`.
@@ -766,7 +766,7 @@ M3 Expressive's navigation rail: collapsed (96px, icon over label) or expanded (
 ```
 
 - `mode`: `collapsed`, `expanded`, `collapsible` (default: expanded until its menu button collapses it; the choice is `$store.rail`, remembered and applied before the first paint), `modal` (collapsed in the layout; the menu button or `$store.rail.show()` opens it expanded over a scrim, focus held until Escape, the scrim or leaving the page), `adaptive` (`<x-app-shell>`'s, one rail per window size class: hidden and opened as a modal on a compact window, collapsed and opened as a modal at `medium`, a standard rail from `expanded` — collapsed there, expanded from `large`).
-- Props: `label` ("Main"), `width` (expanded width, `16rem`, held between 220 and 360px — or the word `narrow` for M3's other *collapsed* width, 80px against the default 96, where the items are their icons alone; the labels stay in the accessibility tree and a narrow rail still expands to 16rem), `align` (`top` default, or `center` for M3's centred destinations — preferred on a tablet; the menu button, brand and FAB stay at the top and the footer at the foot), `menu` (the menu button; on by default for `collapsible`, `modal`, `adaptive`), `divider` (M3's optional vertical divider on the page's side — use it when the page scrolls under a fixed rail), `fill` (`false` for a transparent container, which M3 allows while the items keep 3:1 contrast). Slots: `brand` (beside the menu button, expanded only), `header` (one `<x-fab label icon>`, which the rail morphs into an extended FAB and back as it expands — it also rests at elevation 0, as M3 asks of a nested FAB), the destinations (the only part that scrolls), `footer`. In a flex row the rail sticks to the top of the viewport.
+- Props: `label` ("Main"), `width` (expanded width, `16rem`, held between 220 and 360px — or the word `narrow` for M3's other *collapsed* width, 80px against the default 96, where the items are their icons alone; the labels stay in the accessibility tree and a narrow rail still expands to 16rem), `align` (`top` default, or `center` for M3's centred destinations — preferred on a tablet; the menu button, brand and FAB stay at the top and the footer at the foot), `hide-when-collapsed` (M3's immersive expanded behaviour, `collapsible` and `adaptive` only: collapsing the rail takes it out of the layout instead of narrowing it, and `$store.rail.show()` brings it back expanded over a scrim — so put a menu button in the app bar; the rail's own button then docks it again. Not below `medium` for a collapsible rail nor at `medium` for an adaptive one, where the window rather than the visitor collapses it and M3's collapsed rail may never hide), `menu` (the menu button; on by default for `collapsible`, `modal`, `adaptive`), `divider` (M3's optional vertical divider on the page's side — use it when the page scrolls under a fixed rail), `fill` (`false` for a transparent container, which M3 allows while the items keep 3:1 contrast). Slots: `brand` (beside the menu button, expanded only), `header` (one `<x-fab label icon>`, which the rail morphs into an extended FAB and back as it expands — it also rests at elevation 0, as M3 asks of a nested FAB), the destinations (the only part that scrolls), `footer`. In a flex row the rail sticks to the top of the viewport.
 - Anything else inside a rail takes both shapes with the `rail-collapsed:` variant, true while that rail is drawn collapsed for whatever reason: `<span class="rail-collapsed:hidden">…expanded only…</span>`, `<span class="hidden rail-collapsed:inline-flex">…collapsed only…</span>`. Put the variant on a wrapper, never on a component. Nothing that shows while collapsed may be wider than 96px.
 - A `collapsible` rail is held to the collapsed 96px below `medium` (600px), where M3 says to use a navigation bar rather than a standard rail. `collapsed` and `expanded` are fixed-width by design: wrap one in a `medium:` element if it must not show on a phone.
 - `<x-navigation-rail-item>`: the same props as `<x-navigation-bar-item>`. `<x-navigation-rail-section label="…">`: a group with a heading that shows only while the rail is expanded; it names the group for screen readers either way.