Reveal a cut-off carousel item under reduced motion

Plan step 36 review of a149970d. Reduced motion writes a zero inset for
every item, so isMasked() never called one partly shown and a press on
an item the row cut off did nothing. It now reads the item's box against
the scrollport there, as it already did for multi-aspect, and the
browser test the rewrite added to document the gap asserts the reveal
instead (plan step 32's owed test).

A focused item's inset ring is 3px in again: Tailwind's
-outline-offset-3 is 3px, not the 12px the rewrite wrote.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

tests/Browser/CarouselTest.php

@@ -174,12 +174,10 @@ it('scrolls instantly and leaves every item unmasked under reduced motion', func
             JS));
 });
 
-it('leaves a reduced-motion click on an item cut off at the row\'s edge where it is', function () {
+it('brings an item cut off at the row\'s edge into view when it is pressed under reduced motion', function () {
     // Owed by the Chromium baseline (step 32, docs/plans/material-3-browser-tests.md): reduced
-    // motion writes a zero inset for every item (C-05, so none of them count as masked at all),
-    // and the click-to-reveal affordance gates on that inset, so a press on an item only cut off
-    // by the row's own edge — not by a mask — does not scroll it into view. Documented here, not
-    // fixed: fixing isMasked() for this case is outside a hook rename.
+    // motion writes a zero inset for every item (C-05), so a mask cannot say an item is only partly
+    // shown; carousel.js reads the item's box against the row's instead, as for multi-aspect.
     $page = carouselShowcase(['reducedMotion' => 'reduce'])
         ->assertScript(onCarousel(0, <<<'JS'
             const row = scroller.getBoundingClientRect()
@@ -190,8 +188,10 @@ it('leaves a reduced-motion click on an item cut off at the row\'s edge where it
     $page->script(onCarousel(0, 'items[4].querySelector(\'[data-md-carousel-content]\').click()'));
 
     $page->assertScript(onCarousel(0, <<<'JS'
-        await pause(400)
-        return scroller.scrollLeft === 0
+        await pause(100)
+        const row = scroller.getBoundingClientRect()
+        const item = items[4].getBoundingClientRect()
+        return Math.abs(scroller.scrollLeft) > 0 && item.left >= row.left - 1 && item.right <= row.right + 1
         JS));
 });