fix(mypy): Restore t.cast for MockTranslator in test_nodes.py

why: just watch-mypy uses find to include all .py files, bypassing
pyproject.toml's exclude setting for tests/docs/.
what:
- Restore TYPE_CHECKING import for HTML5Translator
- Restore t.cast calls for MockTranslator arguments

Author: tony

tests/docs/_ext/sphinx_argparse_neo/test_nodes.py

@@ -5,6 +5,9 @@
 import re
 import typing as t
 
+if t.TYPE_CHECKING:
+    from sphinx.writers.html5 import HTML5Translator
+
 import pytest
 from docutils import nodes
 from sphinx_argparse_neo.nodes import (
@@ -469,8 +472,8 @@ def render_argument_to_html(
     node["id_prefix"] = id_prefix
 
     translator = MockTranslator()
-    visit_argparse_argument_html(translator, node)
-    depart_argparse_argument_html(translator, node)
+    visit_argparse_argument_html(t.cast("HTML5Translator", translator), node)
+    depart_argparse_argument_html(t.cast("HTML5Translator", translator), node)
 
     return "".join(translator.body)