docs: add article on Chakra UI + OpenUI

[LC-86]

Fixes #2

This adds a practical implementation-focused article about combining Chakra UI with OpenUI for design-system-aware generative interfaces.

Focus areas:

• exposing a narrow component surface instead of raw primitives
• constraining generation through component vocabulary and prompt rules
• keeping theme awareness inside Chakra-backed components
• validating action surfaces for generated UIs
• using the pairing for real dashboard/support-style app flows rather than toy examples

The article is intentionally written as a product-engineering guide, not a generic introduction.

[vishxrad]

@LC-86 this submission has clear markers of automated generation: branch name codex/openui-chakra-article, AI-style prose throughout the article (one-line paragraph cadence, generic "wisdom" phrasing, no specifics from a real implementation), no screenshots or screen recording, and no demonstration that any of the code was actually run. We can't accept submissions like this. The program is for genuine creator work with the author's voice and visual proof of working code.