fix(web): keep sidebar scrollbar inside inset

packages/client/ui-sidebar/tests/sidebar-styles.spec.ts

@@ -0,0 +1,38 @@
+/** Sidebar shell inset contract shared with the nested workspace browser. */
+import { readFileSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, it } from 'vitest'
+
+const css = readFileSync(fileURLToPath(new URL('../src/client/SidebarRoot.module.css', import.meta.url)), 'utf8')
+
+/**
+ * Declarations of one exact selector, keyed by property.
+ * @param selector - exact selector text.
+ * @returns the normalized declarations, or undefined when absent.
+ */
+function declarations(selector: string): Map<string, string> | undefined {
+  const withoutComments = css.replace(/\/\*[\s\S]*?\*\//g, ' ')
+  for (const [, selectorList = '', body = ''] of withoutComments.matchAll(/([^{}]+)\{([^{}]*)\}/g)) {
+    if (!selectorList.split(',').map(value => value.trim()).includes(selector)) continue
+    const found = new Map<string, string>()
+    for (const part of body.split(';')) {
+      const colon = part.indexOf(':')
+      if (colon === -1) continue
+      found.set(part.slice(0, colon).trim(), part.slice(colon + 1).trim().replace(/\s+/g, ' '))
+    }
+    return found
+  }
+  return undefined
+}
+
+describe('SidebarRoot.module.css inset', () => {
+  it('shares and cancels the wide shell trailing padding structurally', () => {
+    const root = declarations('.root')
+    expect(root?.get('--dsh-sidebar-inline-padding')).toBe('12px')
+    expect(root?.get('padding')).toBe('6px var(--dsh-sidebar-inline-padding)')
+    expect(declarations('.regionArea')?.get('margin-right')).toBe(
+      'calc(-1 * var(--dsh-sidebar-inline-padding))',
+    )
+    expect(declarations('.collapsed .regionArea')?.get('margin-right')).toBe('0')
+  })
+})