[upstream #16342] ClickHouse theme: tab styling

[berry-13]

Found in the ClickHouse theme audit for LibreChat-AI#16342. Rank 8 of 9 by visibility.

Click UI: Click UI tabs are underlined, not filled: padding 0.5rem 0.75rem, top radius 0.25rem, 2px active indicator in #151515 / #faff69, text 400 0.875rem in #696e79 muted and #161517 active (ClickHouse/click-ui@537131f src/components/Tabs/Tabs.module.css:4-27, src/theme/styles/tokens-light.css:1336-1354).

LibreChat under interface.theme: clickhouse: The settings nav uses filled pill items (surface-secondary, 8px radius), and segmented controls such as the agent builder's Skills Off/All/Selected use a raised pill.

Gap class and why it is not in LibreChat-AI#16379: Component redesign: a different tab form, not a value the theme can set. Maintainers' decision; AnimatedTabs.tsx is also stack-owned.

Screenshots (light, dark) are attached below.

[berry-13]

Closing with a documented decision. Click UI draws tabs as underlined text with a 2px active indicator, while LibreChat's settings nav and segmented controls are filled pills. That is a different tab layout, not a value a theme can set, and CLAUDE.md (Theming and styling) keeps themes to data: they may not select alternate feature layouts. So the Click UI underline tab form is intentionally not expressible through the theme. The part that is expressible shipped in LibreChat-AI#16481: the settings nav tabs now draw at the theme control radius (Click UI radii.1, 4px under the ClickHouse theme). Colors on the tabs already follow the theme roles.