Add a 'try it in 5 minutes' sandbox quickstart with a toy repo

[kai-linux]

Goal

Create a minimal quickstart guide that lets someone go from clone to seeing AgentOS dispatch and complete a task in under 5 minutes, using a toy/demo repo. The current quickstart requires config.yaml editing, GitHub Project setup, multiple CLI authentications, and cron configuration before anything happens. Most potential adopters will bounce before completing setup.

Success Criteria

• A make demo or ./demo.sh command that bootstraps a minimal config, creates a test issue, dispatches it, and shows the result
• Works with just a GitHub token (no Telegram, no external objectives)
• Completes in under 5 minutes on a fresh clone
• Output shows the full loop visibly in the terminal
• Documented in README quickstart section

Why This Matters

Activation friction is the #1 killer of GitHub project adoption. If someone can't see value in 5 minutes, they leave. The current setup is a 15-step process before the first task runs.

Outcome Checks

• github_stars