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/fixtures/helpers/AppModeHelper.ts

@@ -68,6 +68,41 @@ export class AppModeHelper {
     await this.comfyPage.nextFrame()
   }
 
+  /**
+   * Inject linearData into the current graph and enter app mode.
+   *
+   * Serializes the graph, injects linearData with the given inputs and
+   * auto-detected output node IDs, then reloads so the appModeStore
+   * picks up the data via its activeWorkflow watcher.
+   *
+   * @param inputs - Widget selections as [nodeId, widgetName] tuples
+   */
+  async enterAppModeWithInputs(inputs: [string, string][]) {
+    await this.page.evaluate(async (inputTuples) => {
+      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))
+
+      const workflow = graph.serialize() as unknown as Record<string, unknown>
+      const extra = (workflow.extra ?? {}) as Record<string, unknown>
+      extra.linearData = { inputs: inputTuples, outputs: outputNodeIds }
+      workflow.extra = extra
+      await window.app!.loadGraphData(
+        workflow as unknown as Parameters<
+          NonNullable<typeof window.app>['loadGraphData']
+        >[0]
+      )
+    }, inputs)
+    await this.comfyPage.nextFrame()
+    await this.toggleAppMode()
+  }
+
   /** The linear-mode widget list container (visible in app mode). */
   get linearWidgets(): Locator {
     return this.page.locator('[data-testid="linear-widgets"]')