Fix table header transparency with opaque background (#18499)

Replace the translucent bg-muted/25 with an opaque color-mix blend
(40% muted on background) to ensure scrolled rows don't show through
the sticky header. Add test coverage for header styling and layout.

src/renderer/src/components/automations/AutomationListTableHeader.test.tsx

@@ -0,0 +1,45 @@
+// @vitest-environment happy-dom
+
+import { cleanup, render, screen } from '@testing-library/react'
+import { afterEach, describe, expect, it } from 'vitest'
+import { AutomationListTableHeader } from './AutomationListTableHeader'
+import {
+  LIST_TABLE_HEADER_CLASS,
+  LIST_TABLE_STICKY_HEADER_CELL_CLASS
+} from '@/lib/list-table-layout'
+
+describe('AutomationListTableHeader', () => {
+  afterEach(cleanup)
+
+  it('renders all expected columns', () => {
+    render(<AutomationListTableHeader />)
+
+    expect(screen.getByText('Name')).toBeDefined()
+    expect(screen.getByText('Schedule')).toBeDefined()
+    expect(screen.getByText('Project')).toBeDefined()
+    expect(screen.getByText('Host')).toBeDefined()
+    expect(screen.getByText('Next run')).toBeDefined()
+    expect(screen.getByText('Last run')).toBeDefined()
+    expect(screen.getByText('Status')).toBeDefined()
+    expect(screen.getByText('Agent')).toBeDefined()
+    expect(screen.getByText('Actions')).toBeDefined()
+  })
+
+  it('uses opaque background and sticky positioning on the header row', () => {
+    const { container } = render(<AutomationListTableHeader />)
+    const header = container.firstElementChild as HTMLElement
+
+    expect(header.className).toContain(LIST_TABLE_HEADER_CLASS)
+    expect(header.className).toContain('sticky')
+    expect(header.className).toContain('top-0')
+    expect(header.className).toContain('bg-[color-mix(in_srgb,var(--muted)_40%,var(--background))]')
+    expect(header.className).not.toContain('bg-muted/25')
+  })
+
+  it('applies sticky cell styling to the first column', () => {
+    render(<AutomationListTableHeader />)
+    const nameCell = screen.getByText('Name')
+
+    expect(nameCell.className).toBe(LIST_TABLE_STICKY_HEADER_CELL_CLASS)
+  })
+})

src/renderer/src/lib/list-table-layout.ts

@@ -5,9 +5,9 @@
  */
 export const LIST_TABLE_CONTAINER_CLASS = 'rounded-md border border-border/50 bg-muted/20'
 
-// Why: z-30 must beat the rows' sticky first cells (z-20) so the header still covers them.
+// Why: z-30 and opaque wash ensure scrolled rows cannot show through the sticky header.
 export const LIST_TABLE_HEADER_CLASS =
-  'sticky top-0 z-30 h-8 items-center gap-3 border-b border-border/50 bg-muted/25 px-3 text-[11px] font-medium uppercase tracking-[0.08em] text-muted-foreground'
+  'sticky top-0 z-30 h-8 items-center gap-3 border-b border-border/50 bg-[color-mix(in_srgb,var(--muted)_40%,var(--background))] px-3 text-[11px] font-medium uppercase tracking-[0.08em] text-muted-foreground'
 
 // Why: keep keyboard-selected rows clear of the sticky table header.
 export const LIST_TABLE_ROW_CLASS =