Refine form control naming and radius in the design library

[qingqing-ux]

Summary

• rename form-style tab components in the design library to semantic Segmented/* names
• document the design-to-code mapping so form segmented controls map to UITabRadioGroup and UITabRadio
• unify the design-library radius of form controls to 4px for Segmented, text-input, search, and standard Select variants

Notes

• this PR is limited to the design library and mapping docs
• no runtime UI code changes are included in this PR

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive 'Design to Code Mapping Guide' to help developers navigate the relationship between design components in builder-component.lib.pen and their Vue implementations in spx-gui. The guide details mapping rules for various UI elements like buttons, resource cards, and editor panels, while also defining token mappings and practical lookup orders. Review feedback identified several sequential numbering errors in the section headings that need to be corrected to maintain proper document structure.

[fennoai]

Clean, focused PR. The Tab/* → Segmented/* rename is complete and consistent, the typo fix (Horizonal → Horizontal) is a nice bonus, and the cornerRadius unification to 4px is applied uniformly across all targeted form controls. The new mapping doc is a valuable reference. A few naming consistency and doc accuracy nits are flagged inline.