docs: MVP guide — Practice & Drill usage, flags, and test notes

[ArchILLtect]

Problem / context

Provide clarity for demo and reviewer.

Proposed solution

• Add projects/mvp/README.md and update docs; include screenshots for flows

In scope / Out of scope

In scope:

• Docs and images
  Out of scope:
• Deep architecture write-ups

Acceptance criteria

• MVP docs added/updated; screenshots included

Area

area:documentation

Dependencies / related issues

Practice and Drill flows complete

Checklist

• I’ve checked existing issues for duplicates.
• I can help implement this and open a PR.