feat(registry): add mk-background — minimal procedural gradient background

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

registry/blocks/mk-background/registry-item.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://hyperframes.heygen.com/schema/registry-item.json",
+  "name": "mk-background",
+  "type": "hyperframes:block",
+  "title": "Minimal Gradient Background",
+  "description": "Procedural soft-blob gradient backdrop in a minimalist presentation style: two radial blobs drifting over a base color, with an animatable rounded-card bar mask and optional frosted-glass mode",
+  "tags": ["background", "gradient", "minimal", "professional", "presentation"],
+  "dimensions": {
+    "width": 1920,
+    "height": 1080
+  },
+  "duration": 10,
+  "files": [
+    {
+      "path": "mk-background.html",
+      "target": "compositions/mk-background.html",
+      "type": "hyperframes:composition"
+    }
+  ]
+}