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/registry.json

@@ -223,26 +223,6 @@
       "name": "transitions-scale",
       "type": "hyperframes:block"
     },
-    {
-      "name": "captions-slam",
-      "type": "hyperframes:block"
-    },
-    {
-      "name": "captions-karaoke",
-      "type": "hyperframes:block"
-    },
-    {
-      "name": "captions-minimal",
-      "type": "hyperframes:block"
-    },
-    {
-      "name": "captions-bounce",
-      "type": "hyperframes:block"
-    },
-    {
-      "name": "captions-cinematic",
-      "type": "hyperframes:block"
-    },
     {
       "name": "vfx-text-cursor",
       "type": "hyperframes:block"
@@ -272,4 +252,4 @@
       "type": "hyperframes:block"
     }
   ]
-}
+}