refactor: Delete isPlainObject type guard and replace its usages with direct typeof checks.

frontend/src/ui/QuickAddMenu.tsx

@@ -1,10 +1,10 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import type { CSSProperties, ReactNode, FormEvent, MutableRefObject } from 'react';
 import { PlusIcon } from './icons';
-import { isPlainObject } from '../utils/typeGuards';
+
 import useFloatingMenu from './useFloatingMenu';
 
-type QuickAddOption = string | number | { id?: string | number; label?: string; name?: string; [key: string]: unknown };
+type QuickAddOption = string | number | { id?: string | number; label?: string; name?: string;[key: string]: unknown };
 
 interface NormalizedOption {
   id?: string | number;
@@ -17,7 +17,7 @@ const normalizeOption = (option: QuickAddOption | null, index: number): Normaliz
   if (option == null) {
     return null;
   }
-  if (isPlainObject(option)) {
+  if (typeof option === 'object') {
     const label = option.label ?? option.name;
     if (label == null) {
       return null;
@@ -190,19 +190,19 @@ const QuickAddMenu = ({
   const menuClassName = 'menu menu--floating';
   const anchoredMenuStyle = isAnchoredMenu && menuStyle
     ? {
-        top: menuStyle.top,
-        left: menuStyle.left,
-        ...(menuStyle.width ? { width: menuStyle.width } : null),
-      }
+      top: menuStyle.top,
+      left: menuStyle.left,
+      ...(menuStyle.width ? { width: menuStyle.width } : null),
+    }
     : undefined;
   const menuInlineStyle = (isAnchoredMenu ? anchoredMenuStyle : menuStyle || undefined) as CSSVarStyle | undefined;
   const hasFloatingWidthVar = Boolean(menuInlineStyle && Object.prototype.hasOwnProperty.call(menuInlineStyle, '--floating-min-width'));
   const menuStyleWithVar: CSSVarStyle | undefined = hasFloatingWidthVar
     ? menuInlineStyle
     : {
-        ...(menuInlineStyle || {}),
-        '--floating-min-width': `${Math.max(menuMinWidth, 0)}px`,
-      };
+      ...(menuInlineStyle || {}),
+      '--floating-min-width': `${Math.max(menuMinWidth, 0)}px`,
+    };
 
   return (
     <div className={className ? `quick-add ${className}` : 'quick-add'}>