ci: run the browser harness on Chromium and Firefox only

nixpkgs' WebKit (WPEWebProcess) aborts on its first page inside the
self-hosted runner VMs, though not on the host with the same sandbox;
its OPFS specs skip on a runtime probe anyway. Re-add --project=webkit
once the abort is understood.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -337,9 +337,13 @@ jobs:
       # renamed export is cheaper to read here than as a blank page.
       - name: The page's calls match the bundle it calls
         run: ./scripts/node-test.sh 'web/tests/bundle/*.test.js'
+      # Chromium and Firefox only, for now. nixpkgs' WebKit (WPEWebProcess)
+      # aborts on its first page inside the runner VMs, though not on the
+      # host; its four specs skip on the OPFS probe anyway, so nothing gated
+      # is lost. Put `--project=webkit` back once that abort is understood.
       - name: Run the harness
         working-directory: harness
-        run: npx playwright test
+        run: npx playwright test --project=chromium --project=firefox
       - if: failure()
         uses: actions/upload-artifact@v7
         with: