UI and React

How the brochure front end is composed: Fluent UI v9, layout/grid tokens, React shell, and error recovery.

Guide	What it covers
Fluent UI v9	Theme, Griffel, components, SSR
Grid and layout	Content column, auto-fit grid, row/columns, container queries
React implementation	Provider chain, Pages Router patterns, error boundary

Related decision record: Fluent UI migration (ADR-0003).