fix: App mode - Widget dropdowns clipped in sidebar (#10338)

## Summary

Popover components for graph mode are appendTo self so scale/translate
works, however in the sidebar this causes them to be clipped by the
parent overflow. This adds a provide/inject flag to change these to be
appended to the body.

## Changes

- **What**: 
- add append to injection for overriding where popovers are mounted
- ensure dropdowns respect this flag
- extract enterAppModeWithInputs helper
- tests

Before:  
<img width="225" height="140" alt="image"
src="https://github.com/user-attachments/assets/bd83b0cd-49a9-45dd-8344-4c10221444fc"
/>

After:  
<img width="238" height="225" alt="image"
src="https://github.com/user-attachments/assets/286e28e9-b37d-4ffc-91a9-7c340757d3fc"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10338-fix-App-mode-Widget-dropdowns-clipped-in-sidebar-3296d73d365081e2ba38e3e82006d65e)
by [Unito](https://www.unito.io)

browser_tests/tests/linearMode.spec.ts

@@ -1,5 +1,3 @@
-import type { Page } from '@playwright/test'
-
 import {
   comfyPageFixture as test,
   comfyExpect as expect
@@ -11,58 +9,10 @@ test.describe('Linear Mode', { tag: '@ui' }, () => {
     await comfyPage.setup()
   })
 
-  async function enterAppMode(comfyPage: {
-    page: Page
-    nextFrame: () => Promise<void>
-  }) {
-    // LinearControls requires hasOutputs to be true. Serialize the current
-    // graph, inject linearData with output node IDs, then reload so the
-    // appModeStore picks up the outputs via its activeWorkflow watcher.
-    await comfyPage.page.evaluate(async () => {
-      const graph = window.app!.graph
-      if (!graph) return
-
-      const outputNodeIds = graph.nodes
-        .filter(
-          (n: { type?: string }) =>
-            n.type === 'SaveImage' || n.type === 'PreviewImage'
-        )
-        .map((n: { id: number | string }) => String(n.id))
-
-      // Serialize, inject linearData, and reload to sync stores
-      const workflow = graph.serialize() as unknown as Record<string, unknown>
-      const extra = (workflow.extra ?? {}) as Record<string, unknown>
-      extra.linearData = { inputs: [], outputs: outputNodeIds }
-      workflow.extra = extra
-      await window.app!.loadGraphData(
-        workflow as unknown as Parameters<
-          NonNullable<typeof window.app>['loadGraphData']
-        >[0]
-      )
-    })
-    await comfyPage.nextFrame()
-
-    // Toggle to app mode via the command which sets canvasStore.linearMode
-    await comfyPage.page.evaluate(() => {
-      window.app!.extensionManager.command.execute('Comfy.ToggleLinear')
-    })
-    await comfyPage.nextFrame()
-  }
-
-  async function enterGraphMode(comfyPage: {
-    page: Page
-    nextFrame: () => Promise<void>
-  }) {
-    await comfyPage.page.evaluate(() => {
-      window.app!.extensionManager.command.execute('Comfy.ToggleLinear')
-    })
-    await comfyPage.nextFrame()
-  }
-
   test('Displays linear controls when app mode active', async ({
     comfyPage
   }) => {
-    await enterAppMode(comfyPage)
+    await comfyPage.appMode.enterAppModeWithInputs([])
 
     await expect(
       comfyPage.page.locator('[data-testid="linear-widgets"]')
@@ -70,7 +20,7 @@ test.describe('Linear Mode', { tag: '@ui' }, () => {
   })
 
   test('Run button visible in linear mode', async ({ comfyPage }) => {
-    await enterAppMode(comfyPage)
+    await comfyPage.appMode.enterAppModeWithInputs([])
 
     await expect(
       comfyPage.page.locator('[data-testid="linear-run-button"]')
@@ -78,7 +28,7 @@ test.describe('Linear Mode', { tag: '@ui' }, () => {
   })
 
   test('Workflow info section visible', async ({ comfyPage }) => {
-    await enterAppMode(comfyPage)
+    await comfyPage.appMode.enterAppModeWithInputs([])
 
     await expect(
       comfyPage.page.locator('[data-testid="linear-workflow-info"]')
@@ -86,13 +36,13 @@ test.describe('Linear Mode', { tag: '@ui' }, () => {
   })
 
   test('Returns to graph mode', async ({ comfyPage }) => {
-    await enterAppMode(comfyPage)
+    await comfyPage.appMode.enterAppModeWithInputs([])
 
     await expect(
       comfyPage.page.locator('[data-testid="linear-widgets"]')
     ).toBeVisible({ timeout: 5000 })
 
-    await enterGraphMode(comfyPage)
+    await comfyPage.appMode.toggleAppMode()
 
     await expect(comfyPage.canvas).toBeVisible({ timeout: 5000 })
     await expect(
@@ -101,7 +51,7 @@ test.describe('Linear Mode', { tag: '@ui' }, () => {
   })
 
   test('Canvas not visible in app mode', async ({ comfyPage }) => {
-    await enterAppMode(comfyPage)
+    await comfyPage.appMode.enterAppModeWithInputs([])
 
     await expect(
       comfyPage.page.locator('[data-testid="linear-widgets"]')