fix(sidebar): SW-2097 keep collapsed SidebarSeparator within the rail

[boramyi-ts]

Sidebar primitive — collapsed separator overflows the rail

In the ui/sidebar.tsx shadcn primitive, SidebarSeparator overrode the base Separator's data-horizontal:w-full with a plain w-auto. tailwind-merge keys those under different variants, so both classes survived and data-horizontal:w-full won — the divider rendered at full rail width plus its mx-2 margins, spilling ~8px past the right edge. In the collapsed icon rail (Components/Sidebar → CollapsedIcon) the line visibly crossed the rail border into the content area and no longer aligned under the icon column.

Measured (collapsed, 47px rail): separator was x: 8 → 55 (width 47, +8px past the rail's right edge of 47).

Fix

Override on the matching variant so tailwind-merge dedupes it:

- className={cn("mx-2 w-auto bg-sidebar-border", className)}
+ className={cn("mx-2 data-horizontal:w-auto bg-sidebar-border", className)}

width: auto (unlike w-full) subtracts the mx-2 margins, so the line sits inset and centered. After: separator is x: 8 → 39 (width 31), centered in the rail under the icon column. This also corrects the (less obvious) slight overflow in the expanded sidebar.

Before / After (collapsed rail, zoomed)

Before	After

In before the line crosses the rail's right border into the content area; in after it's inset within the rail, aligned under the icons.

Verification

• yarn lint — clean (zero warnings)
• yarn typecheck — clean
• yarn test:storybook sidebar — 15/15 pass

Note

Sibling to #153 (SW-2097), which fixes the analogous full-width-divider issue in the DataAppShell composed component. This PR targets the shadcn Sidebar primitive specifically.

🤖 Generated with Claude Code

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
ts-lib-ui-kit-storybook	Ignored		Jun 23, 2026 11:09pm

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🟢	Lines	94.74% (🎯 83%) 🟰 ±0%	20627 / 21770
🟢	Statements	94.74% (🎯 83%) 🟰 ±0%	20627 / 21770
🟢	Functions	93.58% (🎯 74%) 🟰 ±0%	919 / 982
🟢	Branches	88.74% (🎯 81%) 🟰 ±0%	3770 / 4248

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/components/ui/sidebar.tsx	94.28% 🟰 ±0%	77.27% 🟰 ±0%	96.15% 🟰 ±0%	94.28% 🟰 ±0%	50-51, 80, 99-106, 183-206, 563

Generated in workflow #832 for commit 0c7920d by the Vitest Coverage Report Action