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the same unpublished .html path, so it would have shown an empty frame.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

@@ -0,0 +1,80 @@
+{
+  "$schema": "https://hyperframes.heygen.com/schema/registry-item.json",
+  "name": "whip-pan-cut",
+  "type": "hyperframes:component",
+  "title": "Whip Pan Cut",
+  "description": "A full-frame whip pan: scene A whips off laterally with capped directional motion blur while scene B enters in the same direction at matched velocity, on a speed-ramp profile with a decelerating catch. Both scenes ride one strip, so seam velocity is exact by construction. Callers fill the named before/after slot panels; token-styled defaults render when a slot is left empty.",
+  "tags": [
+    "transition",
+    "whip-pan",
+    "motion-blur",
+    "velocity-match",
+    "speed-ramp",
+    "bridge",
+    "slots"
+  ],
+  "jobs": ["bridge"],
+  "family": "transitions",
+  "profile": "transition",
+  "evidence": "Wave K6: the X expert demand study names the whip pan as the loud lateral scene bridge; cut-the-curve donates the transition profile, motion-blur-streak donates the capped directional blur",
+  "syncPoints": [{ "id": "whip-cut", "phase": "in", "offset": 0.53 }],
+  "files": [
+    {
+      "path": "whip-pan-cut.html",
+      "target": "compositions/components/whip-pan-cut.html",
+      "type": "hyperframes:snippet"
+    }
+  ],
+  "variables": [
+    {
+      "id": "direction",
+      "type": "enum",
+      "role": "motion",
+      "label": "Direction",
+      "description": "Shared travel direction for the outgoing and incoming scenes.",
+      "default": "left",
+      "options": [
+        { "value": "left", "label": "Left" },
+        { "value": "right", "label": "Right" }
+      ]
+    },
+    {
+      "id": "whip_at",
+      "type": "number",
+      "role": "timing",
+      "label": "Whip start",
+      "description": "Seconds after mount start when the whip begins.",
+      "default": 0.25,
+      "min": 0,
+      "max": 8,
+      "step": 0.05,
+      "unit": "s"
+    },
+    {
+      "id": "accent",
+      "type": "enum",
+      "role": "style",
+      "label": "Accent",
+      "description": "Seam hairline and default after art tint.",
+      "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 of the landed scene. Default none: it rests until the frame cuts.",
+      "default": "none",
+      "options": [
+        { "value": "none", "label": "None" },
+        { "value": "fade", "label": "Fade" },
+        { "value": "up", "label": "Up" }
+      ]
+    }
+  ]
+}