refactor(core): move PresenceContext to singletons

packages/sanity/src/_singletons/form/studio/PresenceContext.ts

@@ -0,0 +1,4 @@
+import {createContext} from 'react'
+import type {FormNodePresence} from 'sanity'
+
+export const PresenceContext = createContext<FormNodePresence[]>([])

packages/sanity/src/_singletons/index.ts

@@ -18,3 +18,4 @@ export * from './form/inputs/PortableText/PortableTextMemberItemsContext'
 export * from './form/inputs/ReferenceInput/ReferenceItemRefContext'
 export * from './form/studio/DocumentFieldActionsContext'
 export * from './form/studio/FormCallbacksContext'
+export * from './form/studio/PresenceContext'

packages/sanity/src/core/form/studio/contexts/Presence.tsx

@@ -2,13 +2,12 @@
 
 import {type Path} from '@sanity/types'
 import {isEqual, startsWith} from '@sanity/util/paths'
-import {createContext, type ReactNode, useContext, useRef} from 'react'
+import {type ReactNode, useContext, useRef} from 'react'
+import {PresenceContext} from 'sanity/_singletons'
 
 import {type FormNodePresence} from '../../../presence'
 import {immutableReconcile} from '../../store/utils/immutableReconcile'
 
-const PresenceContext = createContext<FormNodePresence[]>([])
-
 export function PresenceProvider(props: {presence: FormNodePresence[]; children: ReactNode}) {
   return (
     <PresenceContext.Provider value={props.presence}>{props.children}</PresenceContext.Provider>