feat(registry): bring back the video-primitive moves (#3169)

Restores the 208 catalog items reverted after their previews 404'd in
production, this time on the payload mechanism rather than the .html files
that caused the outage.

The generator no longer writes a preview document to docs/public. That writer,
and the machinery under it, existed only to produce files the docs host
discards, so it is gone rather than bypassed. Items now embed the composition
itself via a payload, which is what the previous change already does for the
items that were already in the catalog.

The variables explorer is parked, not restored: it drove its preview through
the same unpublished .html path, so it would have shown an empty frame. Items
that declare variables get the live player plus the static variables table, and
reconnecting the explorer to payloads is a follow-up.

registry/components/shared-axis-z/registry-item.json

@@ -0,0 +1,82 @@
+{
+  "$schema": "https://hyperframes.heygen.com/schema/registry-item.json",
+  "name": "shared-axis-z",
+  "type": "hyperframes:component",
+  "title": "Shared Axis Z",
+  "description": "Scale-based shared-axis transition for focus shifts and context depth.",
+  "tags": ["motion-primitive", "remocn-port", "typography"],
+  "files": [
+    {
+      "path": "shared-axis-z.html",
+      "target": "compositions/components/shared-axis-z.html",
+      "type": "hyperframes:snippet"
+    }
+  ],
+  "variables": [
+    {
+      "id": "direction",
+      "type": "enum",
+      "role": "motion",
+      "label": "Direction",
+      "description": "Which way the words travel along the z axis: in swells up from small, out settles down from large.",
+      "default": "in",
+      "options": [
+        {
+          "value": "in",
+          "label": "In"
+        },
+        {
+          "value": "out",
+          "label": "Out"
+        }
+      ]
+    },
+    {
+      "id": "depth",
+      "type": "enum",
+      "role": "motion",
+      "label": "Depth",
+      "description": "Scales how far the words start from their final size, so the push covers a shorter or longer run in the same time.",
+      "default": "standard",
+      "options": [
+        {
+          "value": "shallow",
+          "label": "Shallow"
+        },
+        {
+          "value": "standard",
+          "label": "Standard"
+        },
+        {
+          "value": "deep",
+          "label": "Deep"
+        }
+      ]
+    },
+    {
+      "id": "tone",
+      "type": "enum",
+      "role": "style",
+      "label": "Tone",
+      "description": "Word colour: ink for light frames, paper for dark ones, accent rides --brand.",
+      "default": "ink",
+      "options": [
+        {
+          "value": "ink",
+          "label": "Ink"
+        },
+        {
+          "value": "paper",
+          "label": "Paper"
+        },
+        {
+          "value": "accent",
+          "label": "Accent"
+        }
+      ]
+    }
+  ],
+  "preview": {
+    "poster": "https://static.heygen.ai/hyperframes-oss/docs/images/catalog/components/shared-axis-z.png"
+  }
+}