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/graph.spec.ts

@@ -21,6 +21,6 @@ test.describe('Graph', { tag: ['@smoke', '@canvas'] }, () => {
   test('Validate workflow links', async ({ comfyPage }) => {
     await comfyPage.settings.setSetting('Comfy.Validation.Workflows', true)
     await comfyPage.workflow.loadWorkflow('links/bad_link')
-    await expect(comfyPage.getVisibleToastCount()).resolves.toBe(2)
+    await expect(comfyPage.toast.getVisibleToastCount()).resolves.toBe(2)
   })
 })