refactor: wire helpers into ComfyPage and update test usages

Phase 2 of ComfyPage refactor:

- Add ToastHelper, DragDropHelper, CommandHelper instances to ComfyPage

- Remove migrated methods from ComfyPage (command, toast, dragDrop, workflow, canvasOps, nodeOps methods)

- Update all test files to use new helper paths

- Keep visibleToasts as passthrough getter for backward compatibility

Amp-Thread-ID: https://ampcode.com/threads/T-019c1666-ed27-773c-976a-07cc805d7a6c
Co-authored-by: Amp <amp@ampcode.com>

browser_tests/tests/extensionAPI.spec.ts

@@ -37,7 +37,7 @@ test.describe('Topbar commands', () => {
   test('Should not allow register command defined in other extension', async ({
     comfyPage
   }) => {
-    await comfyPage.registerCommand('foo', () => alert(1))
+    await comfyPage.command.registerCommand('foo', () => alert(1))
     await comfyPage.page.evaluate(() => {
       window['app'].registerExtension({
         name: 'TestExtension1',
@@ -265,7 +265,7 @@ test.describe('Topbar commands', () => {
           })
       })
 
-      await comfyPage.fillPromptDialog('Hello, world!')
+      await comfyPage.nodeOps.fillPromptDialog('Hello, world!')
       expect(await comfyPage.page.evaluate(() => window['value'])).toBe(
         'Hello, world!'
       )