test: improve tox config

tox.ini

@@ -15,6 +15,11 @@ deps =
     camoufox
     -r{toxinidir}/tests/requirements.txt
 extras = ai,shell
+commands_pre =
+    # Install browsers in the tox virtual environment
+    python -m playwright install chromium
+    python -m playwright install-deps chromium firefox
+    python -m camoufox fetch --browserforge
 commands =
     # Run browser tests without parallelization (avoid browser conflicts)
     pytest --cov=scrapling --cov-report=xml -k "DynamicFetcher or StealthyFetcher" --verbose