docs(registry): clarify catalog preview staging and published URLs (#3676)

Co-authored-by: yoma <yingwaizhiying@gmail.com>

Author: jrusso1020

skills-manifest.json

@@ -46,7 +46,7 @@
       "files": 3
     },
     "hyperframes-registry": {
-      "hash": "d6dfcc8ceb7c8178",
+      "hash": "0142a8e09bbe7e2c",
       "files": 12
     },
     "media-use": {

skills/hyperframes-registry/references/contributing.md

@@ -118,9 +118,9 @@ hyperframes snapshot --at "1.0,3.0,5.0,7.0"
 npx hyperframes publish
 ```
 
-**Catalog preview image** — The catalog card uses a PNG at `docs/images/catalog/{kind}/{name}.png` (where `{kind}` is `blocks` or `components`). Generate it from a snapshot, then:
+**Catalog preview image** — For the default PNG preview, save your snapshot at `docs/images/catalog/{kind}/{name}.png` in the repository checkout (`{kind}` is `blocks` or `components`). After upload, the catalog serves it from `https://static.heygen.ai/hyperframes-oss/docs/images/catalog/{kind}/{name}.png`. If `registry-item.json` declares `preview`, the card uses its `poster` URL; a `preview` without `poster` has no image fallback.
 
-- **HeyGen internal contributors:** run `scripts/upload-docs-images.sh` (requires AWS profile `engineering-767398024897`)
+- **HeyGen internal contributors:** run `scripts/upload-docs-images.sh` from the repository root (requires AWS profile `engineering-767398024897`)
 - **External contributors:** attach the preview MP4 to your PR description. A maintainer will generate and upload the catalog image before merging.
 
 ### Step 6: Ship