Add demo GIF to README

- Convert screen recording to optimized GIF (800px width, 15fps)
- Replace ASCII screenshot with animated demo
- Rename section from "Screenshots" to "Demo"

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: NEWBIE0413

README.md

@@ -26,21 +26,9 @@ When you select a project, you won't see a file list - you can only add agents.
 - **Session Modes**: Start new sessions or resume previous ones
 - **Customizable Models**: Add your own CLI tools and commands
 
-## Screenshots
+## Demo
 
-```
-+-------------------+-----------------------------------------------+
-|                   |  [Claude] [Codex] [+]                         |
-|  WORKSPACES       +---------------------+-------------------------+
-|  > my-project     |  Claude             |  Codex                  |
-|    work-stuff     |  $ claude           |  $ codex                |
-|                   |  > Let's build...   |  > Ready to help...     |
-|  ---------------  |                     |                         |
-|  PROJECTS         |                     |                         |
-|  +- frontend/     |                     |                         |
-|  +- backend/      |                     |                         |
-+-------------------+---------------------+-------------------------+
-```
+![SpaceManager Demo](demo.gif)
 
 ## Requirements