feat: sync showcase with WRNexusJS 0.8.72 and @wrnexus/ui 0.8.88

- Sync app, public, scripts, test and examples from the framework's
  component-showcase: redesigned component demos, marketing blocks under
  /blocks, template and preview galleries, distinct Timeline/Section
  variants, Chat Bubble receipts, a top-placement Drawer demo, and the
  playground code panel fix (objects in array props no longer blank out).
- Standalone adaptations kept: the generator and tests read
  component-reference.json from the published @wrnexus/ui, and tests use
  the published @wrnexus/compiler and @wrnexus/syntax.
- Dependencies: every @wrnexus/* package to its latest release (ui 0.8.88,
  styles 0.8.26, core 0.8.16, cli 0.8.72, ...), happy-dom for the
  playground tests, Tailwind 4.3; bun.lock and package-lock.json refreshed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/pages/blocks/section-header.wrn

@@ -0,0 +1,10 @@
+page SectionHeaderBlock {
+ layout = "gallery"
+ 
+ seo { title = "Section Header block" }
+ view { <header class="docs-intro"><a href="/block-library">← All blocks</a><h1>Section Header</h1><p>A ready-to-use section. Copy the complete example below.</p></header><section class="block-live-preview"><SectionHeader eyebrow="Public services" title="Everything citizens need" description="Discover online services, directories, guidance, and verified public information." align="left" size="default" headingLevel="2" maxWidth="3xl" class="showcase-instance showcase-instance--1" /></section><section class="example-code-panel"><header><h2>Copy this example</h2><button type="button" data-copy-target="#example-source">Copy code</button></header><pre><code id="example-source">page SectionHeaderExample <span>&#123;</span>
+  view <span>&#123;</span>
+    &lt;SectionHeader eyebrow="Public services" title="Everything citizens need" description="Discover online services, directories, guidance, and verified public information." align="left" size="default" headingLevel="2" maxWidth="3xl" class="showcase-instance showcase-instance--1" /&gt;
+  <span>&#125;</span>
+<span>&#125;</span></code></pre></section> }
+}