docs: add live demo badge and link to README

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: yarin-mag

README.md

@@ -4,6 +4,10 @@
 
 A dashboard that captures every conversation, token count, and tool call across all your Claude Code agents — automatically, with no changes to your workflow.
 
+[![Live Demo](https://img.shields.io/badge/demo-live-brightgreen)](https://yarin-mag.github.io/Marionette/?demo=true)
+
+> **[Try the live demo →](https://yarin-mag.github.io/Marionette/?demo=true)** — no install required, runs entirely in the browser with mock data.
+
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 ## Quick Start (for users)