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/hooks/useCommandRegistry.ts

@@ -18,6 +18,8 @@ interface CommandRegistryConfig {
   activeTabPath: string | null
   entries: VaultEntry[]
   modifiedCount: number
+  /** Whether the active note has an emoji icon set. */
+  activeNoteHasIcon?: boolean
   mcpStatus?: string
   onInstallMcp?: () => void
   onEmptyTrash?: () => void
@@ -25,6 +27,8 @@ interface CommandRegistryConfig {
   onReindexVault?: () => void
   onReloadVault?: () => void
   onRepairVault?: () => void
+  onSetNoteIcon?: () => void
+  onRemoveNoteIcon?: () => void
 
   onQuickOpen: () => void
   onCreateNote: () => void
@@ -205,6 +209,9 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
     onReindexVault,
     onReloadVault,
     onRepairVault,
+    onSetNoteIcon,
+    onRemoveNoteIcon,
+    activeNoteHasIcon,
   } = config
 
   const hasActiveNote = activeTabPath !== null
@@ -247,6 +254,18 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
         keywords: ['archive'], enabled: hasActiveNote,
         execute: () => { if (activeTabPath) (isArchived ? onUnarchiveNote : onArchiveNote)(activeTabPath) },
       },
+      {
+        id: 'set-note-icon', label: 'Set Note Icon', group: 'Note',
+        keywords: ['icon', 'emoji', 'set', 'add', 'change', 'picker'],
+        enabled: hasActiveNote && !!onSetNoteIcon,
+        execute: () => onSetNoteIcon?.(),
+      },
+      {
+        id: 'remove-note-icon', label: 'Remove Note Icon', group: 'Note',
+        keywords: ['icon', 'emoji', 'remove', 'delete', 'clear'],
+        enabled: hasActiveNote && !!activeNoteHasIcon && !!onRemoveNoteIcon,
+        execute: () => onRemoveNoteIcon?.(),
+      },
 
       // Git
       { id: 'commit-push', label: 'Commit & Push', group: 'Git', keywords: ['git', 'save', 'sync'], enabled: modifiedCount > 0, execute: onCommitPush },
@@ -290,5 +309,6 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
     mcpStatus, onInstallMcp,
     onEmptyTrash, trashedCount,
     onReindexVault, onReloadVault, onRepairVault,
+    onSetNoteIcon, onRemoveNoteIcon, activeNoteHasIcon,
   ])
 }