Rewrite the carousel without Tailwind

Plan step 36 (containment group): <x-carousel>'s and <x-carousel-item>'s
class lists move into resources/css/components/carousel.css and
carousel-item.css, keyed on data-md-carousel (its value is the layout)
and the parts' data-md-carousel-* hooks (-probe, -scroller, -controls
with "auto"/"always", -previous/-next, -item, -surface, -content,
-label/-label-text). Every selector uses a `>` combinator rather than a
bare descendant one, because a carousel item can itself hold a nested
carousel whose own root would otherwise match its parent's layout
rules too (list.css already solves the same problem for segmented
list rows).

Behaviour is unchanged: resources/js/carousel.js (the keyline maths,
C-05's reduced-motion fix, C-11's vertical full-screen layout, C-12's
padding, C-18's item-as-tab-stop, the multi-aspect layout) is touched
only where it reads or writes the renamed hooks and dataset
properties; every inline custom property it writes
(--material-carousel-*) is untouched. The item renders the shared
md-focus-ring class (foundation/interaction.css) instead of a
hand-rolled ring, refined to an inset offset since an outward one
would draw under the neighbouring item. The previous/next buttons
mirror whole in RTL from carousel.css rather than through
<x-icon mirror-rtl>, which <x-button icon> has no prop to reach (a
component outside this batch); the technique matches how the
Tailwind-era markup already mirrored the whole button. The overlay
label's literal white ink over the scrim (C-25) is kept, with the
same reasoning as before.

Hooks renamed data-material-carousel(-item/-surface/-content/-label)
-> data-md-carousel(-item/-surface/-content/-label), data-padding(-end)
-> data-md-padding(-end), data-centered -> data-md-centered, updated in
the same commit: resources/js/carousel.js, tests/Feature/Components/
CarouselTest.php (rewritten on data-md-* and ComponentStylesheet) and
tests/Browser/CarouselTest.php. Browser tests owed by
docs/plans/material-3-browser-tests.md, added but not run: the
multi-aspect carousel's previous/next, arrow keys, Home and End
(scoped by data-md-carousel="multi-aspect" rather than a position in
the showcase, so reordering its examples cannot silently mis-target
the wrong carousel); a reduced-motion click on an item cut off only by
the row's own edge, which documents rather than fixes a real gap —
isMasked()'s inset check is always false once C-05 zeroes every
item's inset, so the click-to-reveal affordance does not fire there
(found by the Chromium baseline, step 32; fixing it is outside a hook
rename).

Imported from the Containment block of components.css.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/css/components/carousel-item.css

@@ -0,0 +1,111 @@
+/*
+ * <x-carousel-item>: one slide of an <x-carousel>, masked and shifted by the keyline maths
+ * carousel.css's header describes, unless the row is full-screen or multi-aspect, where nothing
+ * masks it at all (docs/reference/m3/components-actions-communication-containment.md § Carousel;
+ * docs/audits/m3-alignment/containment.md, C-11, C-12, C-25).
+ *
+ *   [data-md-carousel-item]        the tab stop (C-18), a focusable `group`, `md-focus-ring`
+ *     [data-md-carousel-surface]   the masked, shifted, extra-large-corner (28px) box
+ *       [data-md-carousel-content] the slot (an <img>, cropped)
+ *       [data-md-carousel-label]   the "n of m"-named overlay on the scrim
+ *         [data-md-carousel-label-text]
+ *
+ * The item renders the shared `md-focus-ring` class (foundation/interaction.css) rather than a
+ * hand-rolled ring — the box the class draws *is* the item's own whole hit area — refined here to
+ * an inset ring: an item sits edge to edge with its neighbours in the row, so the class's own 2px
+ * *outward* offset would draw under the next item instead of around this one.
+ *
+ * Full-screen: edge to edge, no corner, no mask — `--material-carousel-shift`/`-inset` go unread.
+ * Multi-aspect: the view writes the item's own `aspect-ratio` inline (`aspect`, a prop, held
+ * inside M3's 9:16–16:9 range); the extra-large corner still applies but nothing masks it, since
+ * an Arrangement describes items of one size and a multi-aspect row has none. Selectors use `>`
+ * throughout, matching carousel.css, so a carousel nested inside an item never inherits its
+ * parent's layout rules.
+ *
+ * The label's ink is a literal `white`, not a role: it sits over `--md-sys-color-scrim`, which is
+ * black in every scheme, theme and contrast level, so white is the one ink that always has the
+ * scrim's contrast — a role (`inverse-on-surface`) is dark ink in a dark scheme and fails there
+ * (C-25, deliberately kept, as the component's original header explained).
+ */
+
+@layer material.reset, material.tokens, material.base, material.layout, material.components, material.text, material.visibility;
+
+@layer material.components {
+    [data-md-carousel-item] {
+        position: relative;
+        height: 100%;
+        flex-shrink: 0;
+        scroll-snap-align: start;
+        scroll-snap-stop: always;
+    }
+
+    [data-md-carousel-item]:focus-visible {
+        outline-offset: -12px;
+    }
+
+    [data-md-carousel='full-screen'] > [data-md-carousel-scroller] > [data-md-carousel-item] {
+        width: 100%;
+    }
+
+    [data-md-carousel='multi-aspect'] > [data-md-carousel-scroller] > [data-md-carousel-item] {
+        width: auto;
+        border-radius: var(--md-sys-shape-corner-xl);
+    }
+
+    [data-md-carousel]:not([data-md-carousel='full-screen']):not([data-md-carousel='multi-aspect']) > [data-md-carousel-scroller] > [data-md-carousel-item] {
+        width: var(--material-carousel-slot);
+        max-width: 100%;
+        border-radius: var(--md-sys-shape-corner-xl);
+    }
+
+    [data-md-carousel-item] > [data-md-carousel-surface] {
+        position: relative;
+        width: 100%;
+        height: 100%;
+        overflow: hidden;
+        background-color: var(--md-sys-color-surface-container-highest);
+        color: var(--md-sys-color-on-surface);
+    }
+
+    [data-md-carousel='multi-aspect'] > [data-md-carousel-scroller] > [data-md-carousel-item] > [data-md-carousel-surface] {
+        border-radius: var(--md-sys-shape-corner-xl);
+    }
+
+    [data-md-carousel]:not([data-md-carousel='full-screen']):not([data-md-carousel='multi-aspect']) > [data-md-carousel-scroller] > [data-md-carousel-item] > [data-md-carousel-surface] {
+        border-radius: var(--md-sys-shape-corner-xl);
+        translate: var(--material-carousel-shift) 0;
+        clip-path: inset(0 var(--material-carousel-inset, 0px) round var(--md-sys-shape-corner-xl));
+    }
+
+    [data-md-carousel-surface] > [data-md-carousel-content] {
+        width: 100%;
+        height: 100%;
+
+        & > img {
+            width: 100%;
+            height: 100%;
+            object-fit: cover;
+        }
+    }
+
+    [data-md-carousel-surface] > [data-md-carousel-label] {
+        pointer-events: none;
+        position: absolute;
+        inset-inline: 0;
+        bottom: 0;
+        display: flex;
+        padding: var(--md-sys-measurement-space500) var(--md-sys-measurement-space200) var(--md-sys-measurement-space200);
+        background: linear-gradient(to top, color-mix(in srgb, var(--md-sys-color-scrim) 60%, transparent), transparent);
+        opacity: var(--material-carousel-label);
+    }
+
+    [data-md-carousel-label] > [data-md-carousel-label-text] {
+        overflow: hidden;
+        color: white;
+        font: var(--md-sys-typescale-title-md);
+        letter-spacing: var(--md-sys-typescale-title-md-tracking);
+        text-overflow: ellipsis;
+        white-space: nowrap;
+        translate: var(--material-carousel-label-shift) 0;
+    }
+}

resources/css/components/carousel.css

@@ -0,0 +1,113 @@
+/*
+ * <x-carousel>: M3 Expressive's carousel — multi-browse, hero, uncontained, the uncontained
+ * multi-aspect-ratio layout (added November 2025) and full-screen, on a native scroll container
+ * with CSS scroll snap. resources/js/carousel.js ports Compose's keyline maths (Arrangement.kt,
+ * Keylines.kt, KeylineList.kt, Strategy.kt, KeylineSnapPosition.kt, Carousel.kt, androidx Compose
+ * Material 3 @ commit 7ac433e44e797de53af85226797862687f37735f, Apache-2.0) and writes the masks
+ * and sizes as inline custom properties every scroll frame; this file draws everything the script
+ * does not — the row's layout per layout, and the controls — and carousel-item.css draws the
+ * item and its mask (docs/reference/m3/components-actions-communication-containment.md
+ * § Carousel; docs/audits/m3-alignment/containment.md).
+ *
+ *   [data-md-carousel]              the row wrapper; its value is the layout
+ *     [data-md-carousel-probe]      hidden, measures the preferred item width for the script
+ *     [data-md-carousel-scroller]   the scroll container (role="region")
+ *       [data-md-carousel-item]     one slide — carousel-item.css
+ *     [data-md-carousel-controls]   previous/next, "auto" (pointer: fine only) or "always"
+ *       [data-md-carousel-previous], [data-md-carousel-next]
+ *
+ * Specs table: 16dp leading/trailing padding, 8dp top/bottom and between items, for every layout
+ * but uncontained (leading only) and full-screen (0, edge to edge — C-12); a `>` combinator
+ * throughout, never a bare descendant one, because a carousel item can itself hold a nested
+ * carousel (a `multi-aspect` gallery inside a `hero` slide) whose own root would otherwise match
+ * its parent's rules too. Full-screen scrolls vertically, one edge-to-edge item at a time, capped
+ * at the 840px medium window it is meant for (C-11); reduced motion needs no rule here at all —
+ * the script writes zero inset, shift and full opacity itself for every layout (C-05).
+ *
+ * The previous/next icons mirror in RTL by scaling the whole button, as the row's arrow keys and
+ * scroll direction already do (`resources/js/carousel.js`'s own `state.rtl`), rather than through
+ * `<x-icon mirror-rtl>`: `<x-button icon>` has no prop to reach it, and flipping a round icon
+ * button whole reads the same as flipping only its glyph.
+ */
+
+@layer material.reset, material.tokens, material.base, material.layout, material.components, material.text, material.visibility;
+
+@import './button.css';
+@import './carousel-item.css';
+
+@layer material.components {
+    [data-md-carousel] {
+        position: relative;
+    }
+
+    [data-md-carousel] > [data-md-carousel-probe] {
+        position: absolute;
+        inset-inline-start: 0;
+        top: 0;
+        height: 0;
+        width: var(--material-carousel-item-width);
+        visibility: hidden;
+        pointer-events: none;
+    }
+
+    [data-md-carousel] > [data-md-carousel-scroller] {
+        display: flex;
+        scrollbar-width: none;
+
+        &::-webkit-scrollbar {
+            display: none;
+        }
+    }
+
+    [data-md-carousel='full-screen'] > [data-md-carousel-scroller] {
+        margin-inline: auto;
+        height: var(--material-carousel-height);
+        max-width: 840px;
+        flex-direction: column;
+        gap: var(--md-sys-measurement-space200);
+        overflow-x: hidden;
+        overflow-y: auto;
+        overscroll-behavior-y: contain;
+        scroll-snap-type: y mandatory;
+    }
+
+    [data-md-carousel]:not([data-md-carousel='full-screen']) > [data-md-carousel-scroller] {
+        height: calc(var(--material-carousel-height) + 16px);
+        gap: var(--md-sys-measurement-space100);
+        overflow-x: auto;
+        overflow-y: hidden;
+        overscroll-behavior-x: contain;
+        padding-block: var(--md-sys-measurement-space100);
+    }
+
+    [data-md-carousel='multi-aspect'] > [data-md-carousel-scroller] {
+        padding-inline-start: var(--material-carousel-pad);
+    }
+
+    [data-md-carousel='multi-browse'] > [data-md-carousel-scroller],
+    [data-md-carousel='hero'] > [data-md-carousel-scroller] {
+        scroll-snap-type: x mandatory;
+    }
+
+    [data-md-carousel] > [data-md-carousel-controls] {
+        display: none;
+        margin-top: 12px;
+        justify-content: flex-end;
+        gap: var(--md-sys-measurement-space100);
+    }
+
+    [data-md-carousel] > [data-md-carousel-controls='always'] {
+        display: flex;
+    }
+
+    @media (pointer: fine) {
+        [data-md-carousel] > [data-md-carousel-controls='auto'] {
+            display: flex;
+        }
+    }
+
+    [data-md-carousel]:not([data-md-carousel='full-screen']) > [data-md-carousel-controls] > [data-md-carousel-previous]:dir(rtl),
+    [data-md-carousel]:not([data-md-carousel='full-screen']) > [data-md-carousel-controls] > [data-md-carousel-next]:dir(rtl) {
+        transform: scaleX(-1);
+    }
+}