feat: add Remotion demo video — 30s product walkthrough

6 animated slides matching the SVG visual identity:
  1. Title (stitch-kit branding)
  2. Problem (what breaks without stitch-kit)
  3. Pipeline (idea → ideate → generate → iterate → convert → ship)
  4. Architecture (5 layers stacking in with skill counts)
  5. Frameworks (7 targets in a grid)
  6. Install CTA (npx command with blinking cursor)

1920x1080, H.264, 30fps, 2.7 MB. Source in demo-video/,
rendered output in .github/assets/demo.mp4.

Author: Gabi

.github/assets/demo.mp4

@@ -4,6 +4,11 @@
 
 # macOS
 .DS_Store
+._*
 
 # Node
 node_modules/
+
+# Remotion demo video — render artifacts
+demo-video/demo.mp4
+demo-video/dist/

.gitignore

@@ -14,6 +14,15 @@ Your agent goes from design-blind to design-competent. You describe what you wan
 
 Works in Claude Code, Codex CLI, and any agent that speaks MCP.
 
+<details>
+<summary><strong>Watch the 30-second demo</strong></summary>
+
+https://github.com/user-attachments/assets/demo-placeholder
+
+*Upload the video: drag `.github/assets/demo.mp4` into a GitHub issue to get a hosted URL, then replace the placeholder above.*
+
+</details>
+
 ---
 
 ## Install