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the same unpublished .html path, so it would have shown an empty frame.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/constellation-hub/registry-item.json

@@ -0,0 +1,72 @@
+{
+  "$schema": "https://hyperframes.heygen.com/schema/registry-item.json",
+  "name": "constellation-hub",
+  "type": "hyperframes:component",
+  "title": "Constellation Hub",
+  "description": "Feature nodes brighten in narration order as real-length SVG connectors draw outward from a fixed central hub, then settle into one lockup.",
+  "tags": ["motion-primitive", "feature-tour", "hub", "nodes", "connector", "reveal"],
+  "jobs": ["exhibit"],
+  "family": "feature-tour",
+  "profile": "network",
+  "evidence": "Wave I I3 constellation-hub contract: fixed hub, ordered feature introductions, and getTotalLength-based connector drawing",
+  "syncPoints": [{ "id": "lockup-settle", "phase": "in", "offset": 2.4 }],
+  "files": [
+    {
+      "path": "constellation-hub.html",
+      "target": "compositions/components/constellation-hub.html",
+      "type": "hyperframes:snippet"
+    }
+  ],
+  "variables": [
+    {
+      "id": "hub_label",
+      "type": "string",
+      "role": "content",
+      "label": "Hub label",
+      "description": "Text displayed inside the fixed central hub.",
+      "default": "Product"
+    },
+    {
+      "id": "nodes",
+      "type": "string",
+      "role": "content",
+      "label": "Feature nodes",
+      "description": "Comma-separated feature labels introduced in narration order.",
+      "default": "Capture,Compose,Render,Share"
+    },
+    {
+      "id": "cues",
+      "type": "string",
+      "role": "timing",
+      "label": "Cues",
+      "description": "Comma-separated seconds (from mount start) for each node reveal. Empty keeps the authored even spread.",
+      "default": ""
+    },
+    {
+      "id": "accent",
+      "type": "enum",
+      "role": "style",
+      "label": "Accent",
+      "description": "Highlight color used by the hub, connectors, and active nodes.",
+      "default": "green",
+      "options": [
+        { "value": "green", "label": "Green" },
+        { "value": "blue", "label": "Blue" },
+        { "value": "violet", "label": "Violet" }
+      ]
+    },
+    {
+      "id": "exit",
+      "type": "enum",
+      "role": "timing",
+      "label": "Exit",
+      "description": "Optional departure. Default none: the lockup holds until the frame cuts.",
+      "default": "none",
+      "options": [
+        { "value": "none", "label": "None" },
+        { "value": "fade", "label": "Fade" },
+        { "value": "up", "label": "Up" }
+      ]
+    }
+  ]
+}