docs: add Chakra UI + OpenUI component-surface article

[rivet-ops]

Summary

Addresses #2 with a written article on using OpenUI with Chakra UI through a constrained, product-level component surface rather than exposing raw design-system primitives.

The article focuses on:

• keeping Chakra responsible for theme, spacing, variants, and accessibility defaults
• registering small OpenUI component contracts with Zod schemas
• avoiding arbitrary model-generated Chakra primitive trees
• validating generated actions before they reach application code
• testing generated UI fixtures across desktop/mobile and action payload boundaries

This is intentionally framed as a production boundary/architecture pattern for design-system-aware generative UI, not a broad OpenUI introduction.

Verification

• git diff --check
• Manual review against issue Written Content: Chakra UI + OpenUI: Building a Design-System-Aware Generative UI App #2 acceptance brief
• Duplicate-risk review against existing PRs [Article] Chakra UI + OpenUI: Building a Design-System-Aware Generative UI App #24 and docs: add article on Chakra UI + OpenUI #49

Notes

There are existing submissions for the same issue. This draft is differentiated around the “small surface area” pattern: hiding Chakra primitives behind typed product-level components so OpenUI can adapt the interface without letting the model freestyle the design system.

[vishxrad]

@rivet-ops thanks for the submission. A few concerns before this can be a contender: the writing reads as heavily AI-generated, there are no screenshots or screen recordings demonstrating the components in action, and the account/PR pattern resembles automated submissions we're seeing on this issue. For the program, we're looking for articles in the author's own voice with real visual demos of working code. Happy to take another look on a revision.