feat(catalog): add Blue Sweater intro showcase (#630)

## Problem

The Blue Sweater intro HyperFrames project was only available as a standalone exported project zip. It was not installable from the public registry or visible in the Catalog Showcases group.

## What this fixes

Adds `blue-sweater-intro-video` as a registry block with its composition, avatar image, and sound mix asset. The block is exposed through the generated catalog page, `docs/public/catalog-index.json`, and the Showcases navigation.

The manifest and generated catalog page credit the creator as [Joe Sai](https://x.com/_blue_sweater_).

## Root cause

Catalog-visible blocks are driven by `registry/registry.json`, each block's `registry-item.json`, generated docs/catalog files, and CDN-hosted preview media. The exported project had a valid standalone composition, but it had not been converted into that registry/catalog contract or uploaded to the docs preview CDN.

## Verification

### Local checks

- `bun install`
- `bun run build`
- `bunx tsx scripts/generate-catalog-pages.ts`
- `bun run generate:catalog-previews -- --only blue-sweater-intro-video`
- `bun packages/cli/src/cli.ts add blue-sweater-intro-video --dir /tmp/hf-blue-sweater-install-test --no-clipboard --json` against a locally served registry
- `bun packages/cli/src/cli.ts lint /tmp/hf-blue-sweater-install-test` returned 0 errors and 3 static GSAP overlap warnings from the supplied timeline/parser path
- `bun packages/cli/src/cli.ts validate /tmp/hf-blue-sweater-install-test --timeout 5000` returned 0 runtime errors and 0 warnings, with contrast audit warnings only
- `bun packages/cli/src/cli.ts inspect /tmp/hf-blue-sweater-install-test --at 0.5,2.5,5.5,9.8,11.2 --json` returned 0 layout issues
- `bun packages/cli/src/cli.ts render /tmp/hf-blue-sweater-install-test --output /tmp/hf-blue-sweater-install-test/blue-sweater-intro-video-render.mp4 --fps 24 --quality draft --workers 3`
- `ffprobe` reported the installed render duration as `12.000000`
- `bunx oxfmt --check registry/registry.json registry/blocks/blue-sweater-intro-video/registry-item.json registry/blocks/blue-sweater-intro-video/blue-sweater-intro-video.html docs/docs.json docs/public/catalog-index.json docs/catalog/blocks/blue-sweater-intro-video.mdx`
- `git diff --check`
- `bunx vitest run packages/cli/src/commands/add.test.ts packages/core/src/registry/types.test.ts`

### Browser verification

- Started a real local HyperFrames preview for the installed test project.
- Used `agent-browser` to open `http://localhost:5198/api/projects/hf-blue-sweater-install-test/preview` at 1920x1080.
- Verified the runtime registered `install-test` and `blue-sweater-intro-video` timelines.
- Sought the block to the final card and verified `@_blue_sweater_` and the following state were visible.
- Recorded an `agent-browser`-driven full animation pass; `ffprobe` confirmed a 1920x1080 WebM with 110 video frames.
- Checked the fresh `agent-browser` session for page errors after the direct preview flow: `errors: []`.
- Used `agent-browser` to load an HTML page with the exact generated CDN `video`/`poster` URLs; the browser reported `readyState: 4`, `videoWidth: 1920`, `videoHeight: 1080`, and `paused: false`.

### CDN upload

Uploaded the generated preview media with AWS CLI to the existing docs image bucket path:

- `s3://heygen-public/hyperframes-oss/docs/images/catalog/blocks/blue-sweater-intro-video.mp4`
- `s3://heygen-public/hyperframes-oss/docs/images/catalog/blocks/blue-sweater-intro-video.png`

Verified both public CDN URLs return `HTTP 200` with correct content type and immutable cache headers:

- `https://static.heygen.ai/hyperframes-oss/docs/images/catalog/blocks/blue-sweater-intro-video.mp4` (`video/mp4`)
- `https://static.heygen.ai/hyperframes-oss/docs/images/catalog/blocks/blue-sweater-intro-video.png` (`image/png`)

## Notes

- Local-only browser proof artifacts:
  - `/tmp/hf-blue-sweater-browser-proof/fresh-final-card.png`
  - `/tmp/hf-blue-sweater-browser-proof/fresh-browser-flow.webm`
  - `/tmp/hf-blue-sweater-cdn-check.png`
- Local-only installed render artifact:
  - `/tmp/hf-blue-sweater-install-test/blue-sweater-intro-video-render.mp4`

.github/workflows/catalog-previews.yml

@@ -7,6 +7,7 @@ on:
       - "registry/blocks/**"
       - "registry/components/**"
       - "scripts/generate-catalog-previews.ts"
+      - ".github/workflows/catalog-previews.yml"
 
 concurrency:
   group: catalog-previews-${{ github.ref }}
@@ -37,9 +38,6 @@ jobs:
         with:
           chrome-version: stable
 
-      # FFmpeg for video encoding
-      - uses: FedericoCarboni/setup-ffmpeg@36c6454b5a2348e7794ba2d82a21506605921e3d # v3
-
       - name: Render changed block/component previews
         run: |
           # Find which blocks/components changed in this PR