cleanup: remove the legacy mask editor and all related code (#7370)

## Summary

Removes the legacy mask editor. May also want to remove the "Beta" tags
on all the current mask editor components/mentions in the app now as
well.

## Context

Telemetry data shows zero users using the legacy mask editor. It has
been considerable time since we switched to the new one, and there
really is no reason to use the legacy version given how lacking it is.

In https://github.com/Comfy-Org/ComfyUI_frontend/pull/7332 (v1.35.2 -
Dec 11, 2025), we added a final warning that the legacy mask editor is
being removed.

On 1.36, this PR can be merged, as more than enough warning will have
been given.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7370-cleanup-remove-the-legacy-mask-editor-and-all-related-code-2c66d73d365081d58fbed0f3c84bcb0d)
by [Unito](https://www.unito.io)

src/extensions/core/maskeditor.ts

@@ -1,26 +1,10 @@
 import _ from 'es-toolkit/compat'
 import type { LGraphNode } from '@/lib/litegraph/src/litegraph'
 
-import { t } from '@/i18n'
-import { useMaskEditor } from '@/composables/maskeditor/useMaskEditor'
-import { useToastStore } from '@/platform/updates/common/toastStore'
 import { app } from '@/scripts/app'
-import { ComfyApp } from '@/scripts/app'
-import { useDialogStore } from '@/stores/dialogStore'
 import { useMaskEditorStore } from '@/stores/maskEditorStore'
-import { ClipspaceDialog } from './clipspace'
-import { MaskEditorDialogOld } from './maskEditorOld'
-
-const warnLegacyMaskEditorDeprecation = () => {
-  const warningMessage = t('toastMessages.legacyMaskEditorDeprecated')
-  console.warn(`[Comfy.MaskEditor] ${warningMessage}`)
-  useToastStore().add({
-    severity: 'warn',
-    summary: 'Alert',
-    detail: warningMessage,
-    life: 4096
-  })
-}
+import { useDialogStore } from '@/stores/dialogStore'
+import { useMaskEditor } from '@/composables/maskeditor/useMaskEditor'
 
 function openMaskEditor(node: LGraphNode): void {
   if (!node) {
@@ -33,56 +17,23 @@ function openMaskEditor(node: LGraphNode): void {
     return
   }
 
-  const useNewEditor = app.extensionManager.setting.get(
-    'Comfy.MaskEditor.UseNewEditor'
-  )
-
-  if (useNewEditor) {
-    useMaskEditor().openMaskEditor(node)
-  } else {
-    warnLegacyMaskEditorDeprecation()
-    // Use old editor
-    ComfyApp.copyToClipspace(node)
-    // @ts-expect-error clipspace_return_node is an extension property added at runtime
-    ComfyApp.clipspace_return_node = node
-    const dlg = MaskEditorDialogOld.getInstance() as any
-    if (dlg?.isOpened && !dlg.isOpened()) {
-      dlg.show()
-    }
-  }
+  useMaskEditor().openMaskEditor(node)
 }
 
 // Check if the dialog is already opened
 function isOpened(): boolean {
-  const useNewEditor = app.extensionManager.setting.get(
-    'Comfy.MaskEditor.UseNewEditor'
-  )
-  if (useNewEditor) {
-    return useDialogStore().isDialogOpen('global-mask-editor')
-  } else {
-    return (MaskEditorDialogOld.instance as any)?.isOpened?.() ?? false
-  }
+  return useDialogStore().isDialogOpen('global-mask-editor')
 }
 
 app.registerExtension({
   name: 'Comfy.MaskEditor',
   settings: [
-    {
-      id: 'Comfy.MaskEditor.UseNewEditor',
-      category: ['Mask Editor', 'NewEditor'],
-      name: 'Use new mask editor',
-      tooltip: 'Switch to the new mask editor interface',
-      type: 'boolean',
-      defaultValue: true,
-      experimental: true
-    },
     {
       id: 'Comfy.MaskEditor.BrushAdjustmentSpeed',
       category: ['Mask Editor', 'BrushAdjustment', 'Sensitivity'],
       name: 'Brush adjustment speed multiplier',
       tooltip:
         'Controls how quickly the brush size and hardness change when adjusting. Higher values mean faster changes.',
-      experimental: true,
       type: 'slider',
       attrs: {
         min: 0.1,
@@ -99,8 +50,7 @@ app.registerExtension({
       tooltip:
         'When enabled, brush adjustments will only affect size OR hardness based on which direction you move more',
       type: 'boolean',
-      defaultValue: true,
-      experimental: true
+      defaultValue: true
     }
   ],
   commands: [
@@ -128,36 +78,7 @@ app.registerExtension({
       label: 'Decrease Brush Size in MaskEditor',
       function: () => changeBrushSize((old) => _.clamp(old - 4, 1, 100))
     }
-  ],
-  init() {
-    // Support for old editor clipspace integration
-    const openMaskEditorFromClipspace = () => {
-      const useNewEditor = app.extensionManager.setting.get(
-        'Comfy.MaskEditor.UseNewEditor'
-      )
-      if (!useNewEditor) {
-        warnLegacyMaskEditorDeprecation()
-        const dlg = MaskEditorDialogOld.getInstance() as any
-        if (dlg?.isOpened && !dlg.isOpened()) {
-          dlg.show()
-        }
-      }
-    }
-
-    const context_predicate = (): boolean => {
-      return !!(
-        ComfyApp.clipspace &&
-        ComfyApp.clipspace.imgs &&
-        ComfyApp.clipspace.imgs.length > 0
-      )
-    }
-
-    ClipspaceDialog.registerButton(
-      'MaskEditor',
-      context_predicate,
-      openMaskEditorFromClipspace
-    )
-  }
+  ]
 })
 
 const changeBrushSize = async (sizeChanger: (oldSize: number) => number) => {