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 The variables explorer is parked, not restored: it drove its preview through the same unpublished .html path, so it would have shown an empty frame.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.
2026-09-07 01:56:04 +00:00 · 2026-08-10 18:46:03 -04:00
parent 0f76305191
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+# cut-the-curve
+
+A velocity-matched directional hard cut. The outgoing subject accelerates along one straight screen vector with `power4.in`; at peak velocity the timeline swaps identities; the incoming subject continues on the same vector and decelerates to rest with `power4.out`. Matched blur and opacity conceal the seam.
+
+Transition profile: no elastic HOLD; retime by changing the mount duration only (0.3s to 3s).
+
+## Variables
+
+| id            | type   | default  | notes                                                                                                                           |
+| ------------- | ------ | -------- | ------------------------------------------------------------------------------------------------------------------------------- |
+| `subject`     | enum   | `cursor` | `cursor`, `card`, or `scene`: the visual payload on both sides of the cut.                                                      |
+| `direction`   | enum   | `left`   | `left`, `right`, `up`, `down`: the shared travel vector.                                                                        |
+| `cutFraction` | number | `0.33`   | Normalized point of the hard cut. The incoming distance derives from it so seam velocity stays matched.                         |
+| `blurPx`      | number | `12`     | Blur shared by both subjects at the seam.                                                                                       |
+| `exit`        | enum   | `none`   | `none` rests until the cut; `fade`/`up` depart the incoming subject over a reserved tail (min(0.35s, 25% of D)) after it lands. |
+
+## Mount
+
+```html
+<div
+  class="clip"
+  data-composition-id="cut-the-curve"
+  data-composition-src="./cut-the-curve.html"
+  data-variable-values='{"subject":"card","direction":"right","cutFraction":0.33}'
+  data-start="0"
+  data-duration="1"
+  data-track-index="0"
+></div>
+```
+
+Elastic root: no `data-width`/`data-height`; it fills whatever box the host clip gives it. Timeline registers under the literal `cut-the-curve` key.
+
+## Notes
+
+- Sync point: the cut lands at `(D - exit tail) * cutFraction`; a `whip-cut` `hf:sfx` CustomEvent fires there for the scene mix stage.
+- Invariants: one shared vector, identity swap only at the cut, matched blur/opacity at the seam. Never split the two halves into independently tuned velocities.