feat(docs): add template gallery page with visual previews (#160)

* feat(docs): add template gallery page with visual previews

* fix(docs): remove invalid MDX heading anchors

* chore: retrigger CI

* feat(docs): merge gallery into templates page with hover-to-play video previews

- Consolidated gallery.mdx and templates.mdx into single templates.mdx
- Moved templates page to Getting Started section
- Added MP4 video previews rendered by hyperframes (hover to play)
- Custom JS for hover-to-play behavior (Mintlify strips JSX event handlers)
- 2-column grid for landscape, 3-column for portrait
- Remotion-style cards with gradient overlay labels

* fix(docs): update broken links after templates page move

* ci(regression): remove scripts/ from regression trigger paths

scripts/ contains dev utilities (lint, versioning, preview generation)
that don't affect the rendering engine.

.github/workflows/regression.yml

@@ -23,7 +23,6 @@ jobs:
               - "packages/core/**"
               - "packages/producer/**"
               - "packages/engine/**"
-              - "scripts/**"
               - "Dockerfile*"
 
   regression-shards: