Create the flagship base-cli consumer application

[codeforester]

Goal

Build the first realistic, installable consumer application for the base-cli framework.

Background

The repository currently contains the standard Base baseline but no application code. It needs one coherent reference consumer that demonstrates how consumer-owned domain logic composes with the Base-CLI lifecycle.

Scope

• Use only the public import base_cli facade.
• Provide a small but credible operational CLI with nested commands and local deterministic fixtures.
• Keep the application runnable offline with a short fresh-clone quickstart.

Acceptance Criteria

• A new user can install the demo and reach a successful command in five minutes.
• The demo runs from the published base-cli package and does not depend on Base.
• The repository includes automated tests for the flagship command paths.
• The README explains which behavior belongs to the demo and which behavior comes from Base-CLI.

Validation

• Run ./tests/validate.sh.
• Run the demo from an installed package environment rather than relying on a source checkout.
• Exercise the documented quickstart and the flagship command tests.

Non-Goals

• Do not add ecosystem catalog, multi-language, cloud-service, or Docker requirements in this issue.
• Do not use private base_cli modules or make Base a runtime dependency.

Project Fields

• Status: Ready
• Priority: P1
• Area: Product
• Initiative: Base-CLI Demo
• Size: M

Agent Assignment

• Assignee: @codeforester