Rewrite the showcase's Chips section without Tailwind

Plan step 38: the Alpine-scope wrapper divs become <x-row>/<x-stack>
carrying x-data directly, giving Filter and Input chips M3's
full-width stretch in place of w-full/space-y-6. The narrow demo that
forces its chip set to scroll moves to a data-md-showcase-chip-scroll
hook (384px, Tailwind's old max-w-sm).

Every id, value and derived aria-label the Chromium ChipsTest
selectors read (#chips, the filter checkboxes' values, "Remove
<email>") is unchanged.

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

resources/css/showcase.css

@@ -390,4 +390,11 @@
         width: 96px;
         height: 96px;
     }
+
+    /* Chips: a row narrow enough that its set has to scroll, to show the fade and the arrow
+       buttons M3 asks an overflowing row for. */
+    [data-md-showcase-chip-scroll] {
+        width: 100%;
+        max-width: 384px;
+    }
 }