test: add regression tests for hyphenated folder sidebar duplicates

- Sidebar unit test: entries with isA 'Monday Ideas' produce exactly
  one section header (not two)
- Playwright smoke test: verify no duplicate section labels in sidebar

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/Sidebar.test.tsx

@@ -893,4 +893,42 @@ describe('Sidebar', () => {
       expect(screen.queryByRole('textbox', { name: 'Section name' })).not.toBeInTheDocument()
     })
   })
+
+  it('renders exactly one section for a hyphenated custom type like Monday Ideas', () => {
+    const entriesWithMondayIdeas: VaultEntry[] = [
+      ...mockEntries,
+      {
+        path: '/vault/monday-ideas/standup-bingo.md',
+        filename: 'standup-bingo.md',
+        title: 'Standup Bingo',
+        isA: 'Monday Ideas',
+        aliases: [], belongsTo: [], relatedTo: [],
+        status: null, owner: null, cadence: null,
+        archived: false, trashed: false, trashedAt: null,
+        modifiedAt: 1700000000, createdAt: null,
+        fileSize: 310, snippet: '', wordCount: 120,
+        relationships: {}, icon: null, color: null, order: null,
+        sidebarLabel: null, template: null, sort: null, view: null,
+        outgoingLinks: [], properties: {},
+      },
+      {
+        path: '/vault/monday-ideas/theme-days.md',
+        filename: 'theme-days.md',
+        title: 'Theme Days',
+        isA: 'Monday Ideas',
+        aliases: [], belongsTo: [], relatedTo: [],
+        status: null, owner: null, cadence: null,
+        archived: false, trashed: false, trashedAt: null,
+        modifiedAt: 1700000000, createdAt: null,
+        fileSize: 280, snippet: '', wordCount: 95,
+        relationships: {}, icon: null, color: null, order: null,
+        sidebarLabel: null, template: null, sort: null, view: null,
+        outgoingLinks: [], properties: {},
+      },
+    ]
+    render(<Sidebar entries={entriesWithMondayIdeas} selection={defaultSelection} onSelect={() => {}} />)
+    // "Monday Ideas" pluralized → "Monday Ideases" (the pluralizeType function)
+    const mondaySections = screen.getAllByText(/Monday Ideas/i)
+    expect(mondaySections).toHaveLength(1)
+  })
 })

tests/smoke/sidebar-duplicate-sections.spec.ts

@@ -0,0 +1,36 @@
+import { test, expect } from '@playwright/test'
+
+test.describe('Sidebar duplicate sections', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.goto('/')
+    await page.waitForLoadState('networkidle')
+  })
+
+  test('no duplicate sidebar section headers', async ({ page }) => {
+    // Verify that every section label in the sidebar is unique.
+    // Before the fix, hyphenated folder names (e.g. monday-ideas/)
+    // would produce a different isA than the Type file title,
+    // resulting in two sidebar sections for the same type.
+
+    const sidebar = page.locator('.app__sidebar')
+
+    // Wait for at least one Expand/Collapse button (indicates sections rendered)
+    await sidebar.locator('button[aria-label*="Collapse"], button[aria-label*="Expand"]').first().waitFor({ timeout: 5000 })
+
+    // Extract section labels from the Expand/Collapse aria-labels
+    const buttons = sidebar.locator('button[aria-label*="Collapse"], button[aria-label*="Expand"]')
+    const count = await buttons.count()
+    const labels: string[] = []
+    for (let i = 0; i < count; i++) {
+      const ariaLabel = await buttons.nth(i).getAttribute('aria-label')
+      // aria-label is like "Collapse Projects" or "Expand Projects"
+      const label = ariaLabel?.replace(/^(Collapse|Expand)\s+/, '') ?? ''
+      if (label) labels.push(label)
+    }
+
+    // Every label should be unique — no duplicates
+    const uniqueLabels = [...new Set(labels)]
+    expect(labels).toEqual(uniqueLabels)
+    expect(labels.length).toBeGreaterThan(0)
+  })
+})