Select on [dir='rtl'] now that no build rewrites :dir()

Plan step 39 (part 4). With Tailwind gone the Workbench's Vite build
still turns every `:dir(rtl)` into a long `:lang()` list (its own CSS
minifier, not Tailwind's doing — confirmed by rebuilding and grepping
the output). Every RTL mirror rule across the eleven stylesheets that
had one now selects `:is([dir='rtl'], [dir='rtl'] *)` instead, matching
`:dir(rtl)`'s own specificity (one pseudo-class) and its inherited
"this element or a descendant of one carrying the attribute" reach; the
built CSS now keeps the selector as written (no `:lang(` or `:dir(` left).

RTL browser tests drop the `lang="ar"` workaround the old rewrite
needed (ContainmentTest's side-sheet probe, LayoutTest's shared
layoutPage() helper) and set only dir="rtl"; CarouselTest's probe
already did. Feature tests asserting the selector's literal text
(Progress, Overlay, Menu, ListDetail, Icon, Carousel) updated to match.

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

resources/css/components/slider.css

@@ -188,7 +188,7 @@
         inset-inline: var(--md-sys-measurement-space25);
         pointer-events: none;
 
-        &:dir(rtl) {
+        &:is([dir='rtl'], [dir='rtl'] *) {
             scale: -1 1;
         }
     }
@@ -254,7 +254,7 @@
             color: var(--slider-on-active);
         }
 
-        &:dir(rtl) {
+        &:is([dir='rtl'], [dir='rtl'] *) {
             scale: -1 1;
         }
     }
@@ -304,7 +304,7 @@
         justify-content: center;
         translate: -50% 0;
 
-        &:dir(rtl) {
+        &:is([dir='rtl'], [dir='rtl'] *) {
             scale: -1 1;
         }
     }