Fix failing test: page-route.spec.ts "should fail navigation when aborting main resource" (Firefox)

## Test Expectation

- **Pattern:** `[page-route.spec.ts] should fail navigation when aborting main resource`
- **Platforms:** all (darwin, linux, win32)
- **Browsers:** Firefox only
- **Mode:** all (headless + headful)
- **Status:** FAIL

Firefox-specific failure.