fix: highlight selected slash suggestion

src/components/PromptInput/PromptInputFooterSuggestions.test.tsx

@@ -0,0 +1,36 @@
+import figures from 'figures'
+import React from 'react'
+import { describe, expect, it } from 'bun:test'
+import { renderToString } from '../../utils/staticRender.js'
+import {
+  PromptInputFooterSuggestions,
+  type SuggestionItem,
+} from './PromptInputFooterSuggestions.js'
+
+describe('PromptInputFooterSuggestions', () => {
+  it('renders a visible marker for the selected suggestion', async () => {
+    const suggestions: SuggestionItem[] = [
+      {
+        id: 'command-help',
+        displayText: '/help',
+        description: 'Show help',
+      },
+      {
+        id: 'command-doctor',
+        displayText: '/doctor',
+        description: 'Run diagnostics',
+      },
+    ]
+
+    const output = await renderToString(
+      <PromptInputFooterSuggestions
+        suggestions={suggestions}
+        selectedSuggestion={1}
+      />,
+      80,
+    )
+
+    expect(output).toContain(`${figures.pointer} /doctor`)
+    expect(output).toContain('  /help')
+  })
+})