Package and publish the demo with a reproducible release workflow

[codeforester]

Summary

Make the demo easy to consume as a versioned reference project while keeping its release lifecycle independent from base-cli.

Scope

• Define the demo package and console entry point.
• Add a lockfile and clean-build validation.
• Publish release notes and a small artifact or source distribution when useful.
• Document how demo releases pin and test the supported base-cli package.

Acceptance criteria

• A clean checkout can reproduce the documented install.
• Release automation verifies tests, documentation examples, and package contents.
• Demo versioning is clearly separate from Base-CLI versioning.

Non-goals

Do not imply that a demo release is an API stability promise for base-cli.