feat(catalog): HyperFrames branding, HTML-in-Canvas guide, remove captions (#647)

* docs: group VFX blocks under HTML-in-Canvas, captions under Captions in sidebar

* docs: add HTML-in-Canvas guide, Chrome flag disclaimer, remove captions

- Add docs/guides/html-in-canvas.mdx — comprehensive guide covering the
  API, feature detection, re-capture patterns, and catalog blocks
- Add Chrome flag Warning banner to every HTML-in-Canvas block page
- Remove captions blocks from registry (will ship separately)
- Add html-in-canvas guide to docs navigation (top of Guides section)

* feat: update liquid glass, portal, shatter with HyperFrames branding

Replace generic placeholder content with HyperFrames-themed text:
- Liquid Glass: 'Ship videos 10x faster' with stats and gradient text
- Portal: 'Write HTML / Render Video' with HyperFrames nav
- Shatter: 'HTML is Video' with render speed/file size metrics

Re-rendered and uploaded preview videos to S3.

registry/blocks/vfx-shatter/vfx-shatter.html

@@ -48,7 +48,7 @@
         color: #fff;
       }
 
-      /* ── Panel A: Introducing v2.0 ─────────────────────────── */
+      /* ── Panel A: Write HTML, Render Video ─────────────────────────── */
       .panel-a-inner {
         width: 100%;
         height: 100%;
@@ -377,7 +377,7 @@
           <div class="panel-a-inner">
             <div class="pa-badge">
               <span class="pa-badge-dot"></span>
-              Introducing v2.0
+              Write HTML, Render Video
             </div>
 
             <h1 class="pa-headline">Everything you loved.<br /><em>Now 10x faster.</em></h1>
@@ -442,7 +442,7 @@
               </div>
             </div>
 
-            <button class="pa-cta">Upgrade Now &rarr;</button>
+            <button class="pa-cta">Start Creating &rarr;</button>
           </div>
         </section>
       </canvas>
@@ -467,26 +467,26 @@
           <div class="panel-b-inner">
             <div class="pb-confetti" id="confetti-container"></div>
 
-            <div class="pb-badge">&#10003; Upgrade Complete</div>
+            <div class="pb-badge">&#10003; Powered by HyperFrames</div>
 
-            <h1 class="pb-headline">You're on v2.0</h1>
+            <h1 class="pb-headline">HTML is Video</h1>
 
             <div class="pb-metrics">
               <div class="pb-metric">
                 <div class="pb-metric-value green">10x</div>
-                <div class="pb-metric-label">Faster</div>
+                <div class="pb-metric-label">Render Speed</div>
               </div>
               <div class="pb-metric">
                 <div class="pb-metric-value blue">50%</div>
-                <div class="pb-metric-label">Smaller</div>
+                <div class="pb-metric-label">File Size</div>
               </div>
               <div class="pb-metric">
                 <div class="pb-metric-value purple">99.99%</div>
-                <div class="pb-metric-label">Uptime</div>
+                <div class="pb-metric-label">Reliability</div>
               </div>
             </div>
 
-            <button class="pb-cta">Explore what's new &rarr;</button>
+            <button class="pb-cta">View Catalog &rarr;</button>
           </div>
         </section>
       </canvas>