Add types-ujson to mypy dependencies for proper ujson type checking

Instead of ignoring import-untyped errors, install types-ujson stubs
to enable proper type checking for ujson imports. This requires adding
type: ignore[no-redef] to the fallback json imports since mypy now
sees both import branches.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: vyasr

.pre-commit-config.yaml

@@ -34,7 +34,7 @@ repos:
     rev: 'v1.13.0'
     hooks:
       - id: mypy
-        additional_dependencies: [types-cachetools, pyarrow-stubs, numpy, pandas-stubs]
+        additional_dependencies: [types-cachetools, types-ujson, pyarrow-stubs, numpy, pandas-stubs]
         args: ["--config-file=pyproject.toml",
                "python/cudf/cudf",
                "python/pylibcudf/pylibcudf",

python/cudf/cudf/io/orc.py

@@ -26,9 +26,9 @@
 from cudf.utils.dtypes import cudf_dtype_from_pa_type, dtype_to_pylibcudf_type
 
 try:
-    import ujson as json  # type: ignore[import-untyped]
+    import ujson as json
 except ImportError:
-    import json
+    import json  # type: ignore[no-redef]
 
 if TYPE_CHECKING:
     from cudf.core.column import ColumnBase

python/cudf/cudf/io/parquet.py

@@ -41,9 +41,9 @@
 from cudf.utils.performance_tracking import _performance_tracking
 
 try:
-    import ujson as json  # type: ignore[import-untyped]
+    import ujson as json
 except ImportError:
-    import json
+    import json  # type: ignore[no-redef]
 
 if TYPE_CHECKING:
     from collections.abc import Callable, Hashable, Sequence