fix: resolve circular dependency by removing comfyPageFixture re-export

- Remove comfyPageFixture re-export from ComfyPage.ts
- Update all test imports to use comfyPageFixture from its own file
- Update README.md example to show correct import path
- Fixes: comfyPageFixture → LocalhostComfyPage → ComfyPage circular import

browser_tests/tests/subgraph.spec.ts

@@ -1,6 +1,6 @@
 import { expect } from '@playwright/test'
 
-import { comfyPageFixture as test } from '../fixtures/ComfyPage'
+import { comfyPageFixture as test } from '../fixtures/comfyPageFixture'
 
 // Constants
 const RENAMED_INPUT_NAME = 'renamed_input'