Analytical surfaces lessons

Module 13 starts with the role explainer and then turns the comparison itself into lesson material.

• analytical-surfaces/L02 compares Evidence, Observable, and Quarto as Tier 1 static file generators. The docs-site verdict is published as the Tier 1 static-surface verdict.
• analytical-surfaces/L04 compares Metabase and Rill as Tier 2 self-hostable BI surfaces. The docs-site verdict is published as the Tier 2 Metabase vs Rill verdict. The winning Metabase deploy is published as the Tier 2 production deploy.
• analytical-surfaces/L06 walks through nao as the Tier 3 conversational / AI-IDE surface. The docs-site lesson is published as the Tier 3 nao walkthrough.

The comparison lessons stay runnable because the authoring experience, operational cost, and failure modes are part of the tutorial evidence.