test/refactor: App mode - Refactor & Save As tests (#10680)

## Summary

Adds e2e Save As tests for #10679.
Refactors tests to remove getByX and other locators in tests to instead
be in fixtures.

## Changes

- **What**: 
- extract app mode fixtures
- add test ids where required
- add new tests

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10680-test-refactor-App-mode-Refactor-Save-As-tests-3316d73d3650815b9d49ccfbb6d54416)
by [Unito](https://www.unito.io)

browser_tests/fixtures/helpers/WorkflowHelper.ts

@@ -1,5 +1,6 @@
 import { readFileSync } from 'fs'
 
+import type { AppMode } from '../../../src/composables/useAppMode'
 import type {
   ComfyApiWorkflow,
   ComfyWorkflowJSON
@@ -104,6 +105,40 @@ export class WorkflowHelper {
     })
   }
 
+  async getActiveWorkflowPath(): Promise<string | undefined> {
+    return this.comfyPage.page.evaluate(() => {
+      return (window.app!.extensionManager as WorkspaceStore).workflow
+        .activeWorkflow?.path
+    })
+  }
+
+  async getActiveWorkflowActiveAppMode(): Promise<AppMode | null | undefined> {
+    return this.comfyPage.page.evaluate(() => {
+      return (window.app!.extensionManager as WorkspaceStore).workflow
+        .activeWorkflow?.activeMode
+    })
+  }
+
+  async getActiveWorkflowInitialMode(): Promise<AppMode | null | undefined> {
+    return this.comfyPage.page.evaluate(() => {
+      return (window.app!.extensionManager as WorkspaceStore).workflow
+        .activeWorkflow?.initialMode
+    })
+  }
+
+  async getLinearModeFromGraph(): Promise<boolean | undefined> {
+    return this.comfyPage.page.evaluate(() => {
+      return window.app!.rootGraph.extra?.linearMode as boolean | undefined
+    })
+  }
+
+  async getOpenWorkflowCount(): Promise<number> {
+    return this.comfyPage.page.evaluate(() => {
+      return (window.app!.extensionManager as WorkspaceStore).workflow.workflows
+        .length
+    })
+  }
+
   async isCurrentWorkflowModified(): Promise<boolean | undefined> {
     return this.comfyPage.page.evaluate(() => {
       return (window.app!.extensionManager as WorkspaceStore).workflow