refactor: use useMemo instead of useCallback for groups builder in CommandPalette

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

frontend/src/components/layout/CommandPalette.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect, useRef, useCallback } from 'react'
+import { useState, useEffect, useRef, useCallback, useMemo } from 'react'
 import { useNavigate } from 'react-router-dom'
 import {
   Search, Loader2, ArrowRight, FileText, Clock,
@@ -136,7 +136,7 @@ export function CommandPalette({ open, onClose }: CommandPaletteProps) {
   }, [query])
 
   // Build groups based on intent and search results
-  const groups = useCallback((): Group[] => {
+  const builtGroups = useMemo((): Group[] => {
     const trimmed = query.trim()
     const intent = detectIntent(trimmed)
     const lower = trimmed.toLowerCase()
@@ -243,8 +243,6 @@ export function CommandPalette({ open, onClose }: CommandPaletteProps) {
     return result
   }, [query, searchFlows, searchSessions, user])
 
-  const builtGroups = groups()
-
   // Flatten all items for keyboard navigation
   const flatItems: PaletteItem[] = builtGroups.flatMap(g => g.items)