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/fixtures/ComfyPage.ts

@@ -1591,7 +1591,6 @@ export abstract class ComfyPage {
 
 // Re-export shared constants and fixture
 export { testComfySnapToGridGridSize } from './constants'
-export { comfyPageFixture } from './comfyPageFixture'
 
 const makeMatcher = function <T>(
   getValue: (node: NodeReference) => Promise<T> | T,