ENG-10641: Document AI Builder Design System feature

[carlosabadia]

No description provided.

[linear-code]

ENG-10641

[chatgpt-codex-connector]

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[greptile-apps]

Greptile Summary

Adds documentation for AI Builder Design Systems and updates docs navigation behavior.

• Registers the new Design Systems page in the AI Builder sidebar.
• Distinguishes basename-relative router links from raw cross-app and external anchors.
• Adds regression coverage for navbar link classification and destinations.

Confidence Score: 5/5

The pull request appears safe to merge.

The new documentation is correctly discovered and registered, while the navbar changes consistently preserve basename-aware routing for internal links and full-path navigation for cross-app and external links.

Important Files Changed

Filename	Overview
docs/ai_builder/features/design_systems.md	Adds a complete Design Systems feature guide that follows existing markdown page discovery conventions.
docs/app/reflex_docs/templates/docpage/sidebar/sidebar_items/ai.py	Adds the automatically generated Design Systems route to the AI Builder feature sidebar.
docs/app/reflex_docs/views/docs_navbar.py	Uses router links for in-app destinations and raw anchors for external or cross-app destinations.
docs/app/tests/test_docs_navbar.py	Adds focused regression tests covering internal, cross-app, and off-site navbar link behavior.

_{Reviews (1): Last reviewed commit: "ENG-10641: Document AI Builder Design Sy..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing carlos/add-design-systems-docs (6bea5a7) with main (1358e00)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩