Rewrite the showcase's Progress section without Tailwind

Plan step 38: the "bind" example's wrapper div becomes <x-stack>/
<x-row>, and the one enlarged circular indicator moves to a
data-md-showcase-progress-lg hook. Along the way, $examples changes
from a ['Title' => [code, stack]] tuple back to the plain
'Title' => <<<'BLADE' every other section uses, with the row
exceptions listed separately: the tuple's leading `[` broke
Sections::index()'s regex, so every one of this section's examples
was silently missing from the showcase search index. Fixing the shape
recovers them — the Feature ShowcaseTest's search-index assertion
count moves from 259 to 266.

Every aria-label the Chromium ProgressTest reads off #progress
(Linear, Circular, Circular wavy, Bound, the indeterminate variants)
is unchanged.

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

resources/css/showcase.css

@@ -383,4 +383,11 @@
     [data-md-showcase-illustration='on-accent'] {
         fill: var(--md-sys-color-on-tertiary);
     }
+
+    /* Progress: one circular indicator drawn larger than its 48px default, to show the ring
+       scales with its box. */
+    [data-md-showcase-progress-lg] {
+        width: 96px;
+        height: 96px;
+    }
 }