test(theme): add unit tests for theme constants

client/src/__tests__/theme.test.ts

@@ -0,0 +1,12 @@
+import { describe, expect, it } from 'vitest'
+import { getThemeMode, THEMES } from '../theme.ts'
+
+describe('theme catalog', () => {
+  it('uses forest as the default theme', () => {
+    expect(getThemeMode()).toBe('forest')
+  })
+
+  it('does not expose removed Ocean or Nordic themes', () => {
+    expect(Object.keys(THEMES)).toEqual(['midnight', 'garden', 'forest', 'arctic'])
+  })
+})