Frontend: site chrome, demo shell, pages, and the contract gates

Five parallel lanes plus an integration pass. The header, gallery, router and
sitemap are all generated from the demo registry, so adding src/demos/<slug>/
puts a demo everywhere with zero edits to shared files — which is the whole
reason demo nine cannot break demo one.

check-demos enforces the twelve contract rules: 142 checks over one live demo.
Two worth naming. The shell may not mention a specific slug, because an
'if (slug === wordle)' in src/components/demo/ is a contract bug wearing a
patch. And a spec-status demo must ship a real specification — task, actions,
grader, counterweight, eval command — since a coming-soon card reads worse than
an honest empty gallery.

Bundle budget holds: entry 108.79 kB gzipped against a 160 kB ceiling, the demo
chunk 21.15 kB against 90 kB. recharts is 108 kB gzipped and lives behind a lazy
import so it never touches the entry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019mt6sHQHEnEYrJZvoMCJSB

src/components/demo/DemoErrorBoundary.tsx

@@ -1,6 +1,7 @@
 import { Component } from 'react';
 import type { ErrorInfo, ReactNode } from 'react';
 import { AlertTriangle, ExternalLink, RotateCcw } from 'lucide-react';
+import { Button } from '@/components/ui/button';
 
 const REPO_URL = 'https://github.com/karti-ai/PIG-Demo';
 
@@ -54,7 +55,7 @@ export class DemoErrorBoundary extends Component<DemoErrorBoundaryProps, DemoErr
     return (
       <div role="alert" className="card mx-auto my-10 max-w-xl p-6">
         <div className="flex items-center gap-2 text-warning">
-          <AlertTriangle className="h-5 w-5" aria-hidden="true" />
+          <AlertTriangle className="size-5" aria-hidden="true" />
           <h2 className="text-base font-semibold">
             {demoTitle ? `${demoTitle} failed to render` : 'This demo failed to render'}
           </h2>
@@ -68,21 +69,16 @@ export class DemoErrorBoundary extends Component<DemoErrorBoundaryProps, DemoErr
           {error.message || 'Unknown error'}
         </p>
         <div className="mt-5 flex flex-wrap gap-2">
-          <button
-            type="button"
-            onClick={this.handleReset}
-            className="tap inline-flex items-center gap-2 rounded-lg bg-primary px-4 py-2 text-sm font-medium text-primary-foreground transition-colors duration-2 ease-enter hover:bg-primary/90"
-          >
-            <RotateCcw className="h-4 w-4" aria-hidden="true" />
+          <Button size="touch" onClick={this.handleReset}>
+            <RotateCcw aria-hidden="true" />
             Try again
-          </button>
-          <a
-            href={sourceHref ?? REPO_URL}
-            className="tap inline-flex items-center gap-2 rounded-lg border border-border px-4 py-2 text-sm font-medium transition-colors duration-2 ease-enter hover:bg-surface-2"
-          >
-            Read the source
-            <ExternalLink className="h-4 w-4" aria-hidden="true" />
-          </a>
+          </Button>
+          <Button variant="outline" size="touch" asChild>
+            <a href={sourceHref ?? REPO_URL} rel="noreferrer">
+              Read the source
+              <ExternalLink aria-hidden="true" />
+            </a>
+          </Button>
         </div>
       </div>
     );