feat(ui): migrate the page and section components, add the layout tour

Section, SectionHeader and PublicPageShell move onto wire-* classes with
local style blocks, variants as data attributes. SectionHeader loses 38
utility lines, and Section stops spending one line per variant and colour
pairing: tinted and solid now select on two attributes. PageHeader was already
on the convention and only needed the audit.

examples/basic-app/app/pages/layout.wrn composes the whole set into one page.

Building it surfaced a library-wide bug. Ten custom properties were referenced
by components and defined by nothing: --wire-color-focus, --wire-color-surface-soft,
--wire-color-on-danger, --wire-color-surface-subtle and the input-* family,
plus hover and contrast for every semantic colour except primary and
secondary. An undefined custom property does not warn, it resolves to nothing,
so focus rings drew with no colour and every soft surface rendered
transparent -- 27 components referenced surface-soft alone. They are derived
in the theme now, and a test checks every token a component references against
the rendered theme CSS rather than the source, since most are generated.

The semantic spread also had to move ahead of the primary and secondary
entries so the palette keeps winning for those two.

Known and unresolved: LayoutSplitter emits its sizeChange output and the
component does fire it, but a parent binding on the tag is not invoked. The
tour page therefore points at the handle aria-valuenow rather than wiring a
handler that would never update. Outputs work elsewhere, so this is narrower
than an outputs-are-broken problem and needs its own investigation.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

examples/component-showcase/app/pages/components/layout-splitter.wrn

@@ -25,7 +25,7 @@ page LayoutSplitterDetail {
       </div>
       <div class="detail-hero-icon"><span class="icon-[lucide--component] size-10" aria-hidden="true"></span></div>
     </header>
-    <section id="playground" class="detail-section playground-section" data-playground data-playground-component="LayoutSplitter" data-playground-public-tag="true" data-playground-has-slot="true" data-playground-events="resize">
+    <section id="playground" class="detail-section playground-section" data-playground data-playground-component="LayoutSplitter" data-playground-public-tag="true" data-playground-has-slot="true" data-playground-events="sizeChange">
       <div class="detail-section-heading"><span>Interactive playground</span><h2>Configure Layout Splitter</h2><p>Change any prop and inspect the server-rendered component immediately.</p></div>
       <div class="playground-workbench">
         <div class="playground-preview">
@@ -110,14 +110,14 @@ page LayoutSplitterDetail {
           </section>
         </div>
       </article></div></section>
-        <section id="events" class="detail-section"><div class="detail-section-heading"><span>Component outputs</span><h2>Receive every typed component output</h2><p>Use declarative output handlers in <code>.wrn</code> files or register a direct output handler from JavaScript. The canonical API exposes <code>payload</code> and does not require <code>event.detail</code>.</p></div><div class="detail-events-grid"><div class="detail-events-list"><div><code>@resize</code><span>Fires when the component emits the resize event.</span></div></div><div class="detail-event-examples"><section class="demo-code"><header><span><span class="icon-[lucide--braces] size-4" aria-hidden="true"></span>Declarative handlers</span><small>.wrn</small></header><pre><code>&lt;LayoutSplitter
-  @resize='console.log(payload)'
+        <section id="events" class="detail-section"><div class="detail-section-heading"><span>Component outputs</span><h2>Receive every typed component output</h2><p>Use declarative output handlers in <code>.wrn</code> files or register a direct output handler from JavaScript. The canonical API exposes <code>payload</code> and does not require <code>event.detail</code>.</p></div><div class="detail-events-grid"><div class="detail-events-list"><div><code>@sizeChange</code><span>Fires when the component emits the sizeChange event.</span></div></div><div class="detail-event-examples"><section class="demo-code"><header><span><span class="icon-[lucide--braces] size-4" aria-hidden="true"></span>Declarative handlers</span><small>.wrn</small></header><pre><code>&lt;LayoutSplitter
+  @sizeChange='console.log(payload)'
 /&gt;</code></pre></section><section class="demo-code"><header><span><span class="icon-[lucide--radio] size-4" aria-hidden="true"></span>Direct output handlers</span><small>.js</small></header><pre><code>import <span>&#123;</span> registerOutputHandler <span>&#125;</span> from "@wrnexus/csr/outputs"
 
 const component = document.querySelector("[data-ui-component=\"LayoutSplitter\"], [data-component=\"LayoutSplitter\"]")
 
-if (component) registerOutputHandler(component, "resize", (payload) =&gt; <span>&#123;</span>
-  console.log("resize", payload)
+if (component) registerOutputHandler(component, "sizeChange", (payload) =&gt; <span>&#123;</span>
+  console.log("sizeChange", payload)
 <span>&#125;</span>)</code></pre></section></div></div></section>
         <section id="api" class="detail-section"><div class="detail-section-heading"><span>Component API</span><h2>Props and configuration</h2><p>All content and behavior shown above is supplied through these props and slots.</p></div><div class="docs-table-wrap"><table class="docs-table"><thead><tr><th>Prop</th><th>Type</th><th>Default</th><th>Required</th></tr></thead><tbody><tr><td><code>color</code></td><td>string</td><td><code>"primary"</code></td><td>No</td></tr><tr><td><code>size</code></td><td>number</td><td><code>50</code></td><td>No</td></tr><tr><td><code>orientation</code></td><td>string</td><td><code>"horizontal"</code></td><td>No</td></tr><tr><td><code>minSize</code></td><td>number</td><td><code>15</code></td><td>No</td></tr><tr><td><code>step</code></td><td>number</td><td><code>5</code></td><td>No</td></tr><tr><td><code>label</code></td><td>string</td><td><code>"Resize panels"</code></td><td>No</td></tr><tr><td><code>class</code></td><td>string</td><td><code>""</code></td><td>No</td></tr></tbody></table></div></section>
       </main>

examples/component-showcase/showcase-manifest.json

@@ -693,7 +693,7 @@
       "demoCount": 2,
       "propCount": 7,
       "slots": ["start", "end", "default"],
-      "events": ["resize"],
+      "events": ["sizeChange"],
       "profiled": true
     },
     {