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the same unpublished .html path, so it would have shown an empty frame.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

@@ -0,0 +1,73 @@
+{
+  "$schema": "https://hyperframes.heygen.com/schema/registry-item.json",
+  "name": "particle-image-reveal",
+  "type": "hyperframes:component",
+  "title": "Particle Image Reveal",
+  "description": "A seeded deterministic particle field converges and settles while a slotted image reveals beneath it, the trail thinning until the image holds clean.",
+  "tags": ["motion-primitive", "intros-reveals", "particles", "reveal", "canvas", "deterministic"],
+  "jobs": ["reveal"],
+  "family": "intros-reveals",
+  "profile": "materialize",
+  "evidence": "Wave K3 demand slate: seeded-table canvas particles, pure function of (index, time), redraw on every eventful seek",
+  "syncPoints": [{ "id": "image-locked", "phase": "in", "offset": 2.8 }],
+  "files": [
+    {
+      "path": "particle-image-reveal.html",
+      "target": "compositions/components/particle-image-reveal.html",
+      "type": "hyperframes:snippet"
+    }
+  ],
+  "variables": [
+    {
+      "id": "density",
+      "type": "enum",
+      "role": "style",
+      "label": "Density",
+      "description": "Particle count for the converging field.",
+      "default": "med",
+      "options": [
+        { "value": "low", "label": "Low" },
+        { "value": "med", "label": "Medium" },
+        { "value": "high", "label": "High" }
+      ]
+    },
+    {
+      "id": "direction",
+      "type": "enum",
+      "role": "timing",
+      "label": "Direction",
+      "description": "ltr sweeps the reveal left to right; center opens an iris from the middle outward.",
+      "default": "ltr",
+      "options": [
+        { "value": "ltr", "label": "Left to right" },
+        { "value": "center", "label": "Center out" }
+      ]
+    },
+    {
+      "id": "accent",
+      "type": "enum",
+      "role": "style",
+      "label": "Accent",
+      "description": "Particle and monogram color: green rides --brand, blue rides --accent, violet rides --accent-2.",
+      "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 revealed image holds until the frame cuts.",
+      "default": "none",
+      "options": [
+        { "value": "none", "label": "None" },
+        { "value": "fade", "label": "Fade" },
+        { "value": "up", "label": "Up" }
+      ]
+    }
+  ]
+}