Run the MCP quarantine demo locally

[peycheff-com]

The most compact public demo for HELM right now is the MCP quarantine path:

git clone https://github.com/Mindburn-Labs/helm-ai-kernel.git
cd helm-ai-kernel
make build
bash scripts/launch/demo-mcp.sh

Expected proof points:

• unknown MCP server -> DENY
• unknown MCP tool -> DENY
• missing schema pin -> DENY
• schema-pinned local fixture call -> ALLOW
• no fixture dispatch for unknown tools or servers

The sanitized transcript lives at examples/launch/assets/mcp-quarantine.transcript.txt, and the README now includes a visual proof asset for this path.