test(docs[sphinx_fonts]): add mypy ignore-errors directive

why: sphinx_fonts tests use SimpleNamespace as duck-typed Sphinx app,
causing arg-type or import-not-found errors depending on mypy config.
what:
- Add mypy: ignore-errors file-level directive to test_sphinx_fonts.py

Author: tony

tests/docs/_ext/test_sphinx_fonts.py

@@ -1,5 +1,7 @@
 """Tests for sphinx_fonts Sphinx extension."""
 
+# mypy: ignore-errors
+
 from __future__ import annotations
 
 import logging