feat: add emoji icon picker for notes stored in frontmatter

Every note can now have an optional emoji icon (frontmatter `icon` field).
The icon is displayed in the editor header, note list, search results,
and Quick Open. Includes command palette commands "Set Note Icon" and
"Remove Note Icon", plus full test coverage (Vitest + Playwright).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/NoteIcon.test.tsx

@@ -0,0 +1,78 @@
+import { describe, it, expect, vi } from 'vitest'
+import { render, screen, fireEvent, act } from '@testing-library/react'
+import { NoteIcon } from './NoteIcon'
+
+describe('NoteIcon', () => {
+  it('shows add button when no icon is set', () => {
+    render(<NoteIcon icon={null} onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    expect(screen.getByTestId('note-icon-add')).toBeInTheDocument()
+    expect(screen.queryByTestId('note-icon-display')).not.toBeInTheDocument()
+  })
+
+  it('displays the emoji when icon is set', () => {
+    render(<NoteIcon icon="🎯" onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    expect(screen.getByTestId('note-icon-display')).toHaveTextContent('🎯')
+    expect(screen.queryByTestId('note-icon-add')).not.toBeInTheDocument()
+  })
+
+  it('does not display Phosphor icon names as emoji', () => {
+    render(<NoteIcon icon="rocket" onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    // Phosphor icon name is not an emoji → shows add button
+    expect(screen.getByTestId('note-icon-add')).toBeInTheDocument()
+  })
+
+  it('opens emoji picker when add button is clicked', () => {
+    render(<NoteIcon icon={null} onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    fireEvent.click(screen.getByTestId('note-icon-add'))
+    expect(screen.getByTestId('emoji-picker')).toBeInTheDocument()
+  })
+
+  it('shows change/remove menu when existing icon is clicked', () => {
+    render(<NoteIcon icon="🔥" onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    fireEvent.click(screen.getByTestId('note-icon-display'))
+    expect(screen.getByTestId('note-icon-menu')).toBeInTheDocument()
+    expect(screen.getByTestId('note-icon-change')).toBeInTheDocument()
+    expect(screen.getByTestId('note-icon-remove')).toBeInTheDocument()
+  })
+
+  it('calls onRemoveIcon when Remove is clicked', () => {
+    const onRemove = vi.fn()
+    render(<NoteIcon icon="🔥" onSetIcon={() => {}} onRemoveIcon={onRemove} />)
+    fireEvent.click(screen.getByTestId('note-icon-display'))
+    fireEvent.click(screen.getByTestId('note-icon-remove'))
+    expect(onRemove).toHaveBeenCalledOnce()
+  })
+
+  it('opens picker when Change is clicked from menu', () => {
+    render(<NoteIcon icon="🔥" onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    fireEvent.click(screen.getByTestId('note-icon-display'))
+    fireEvent.click(screen.getByTestId('note-icon-change'))
+    expect(screen.getByTestId('emoji-picker')).toBeInTheDocument()
+  })
+
+  it('calls onSetIcon when emoji is selected from picker', () => {
+    const onSet = vi.fn()
+    render(<NoteIcon icon={null} onSetIcon={onSet} onRemoveIcon={() => {}} />)
+    fireEvent.click(screen.getByTestId('note-icon-add'))
+    const emojiButtons = screen.getAllByTestId('emoji-option')
+    fireEvent.click(emojiButtons[0])
+    expect(onSet).toHaveBeenCalledOnce()
+  })
+
+  it('hides add button when not editable', () => {
+    render(<NoteIcon icon={null} editable={false} onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    expect(screen.queryByTestId('note-icon-add')).not.toBeInTheDocument()
+  })
+
+  it('disables icon click when not editable', () => {
+    render(<NoteIcon icon="🎯" editable={false} onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    const display = screen.getByTestId('note-icon-display')
+    expect(display).toBeDisabled()
+  })
+
+  it('opens picker on laputa:open-icon-picker event', () => {
+    render(<NoteIcon icon={null} onSetIcon={() => {}} onRemoveIcon={() => {}} />)
+    act(() => { window.dispatchEvent(new CustomEvent('laputa:open-icon-picker')) })
+    expect(screen.getByTestId('emoji-picker')).toBeInTheDocument()
+  })
+})