fix: add to_lance() and to_polars() stub methods for type-checkers (#2876)

Adds `Table.to_lance()` and `Table.to_polars()` methods (non-abstract
methods, defaulting to `NotImplementedError`) so type checkers like
mypy, pyright and ty don’t flag them as unknown attributes on `Table`.
Not making these abstract methods should keep existing remote/other
`Table` implementations instantiable.

This is non-breaking change to existing functionality and is purely for
the purpose of pleasing static type-checkers like mypy, ty and pyright.

<img width="626" height="134" alt="image"
src="https://github.com/user-attachments/assets/f4619bca-a882-432b-bd23-ae8f189ff9e3"
/>

python/python/lancedb/table.py

@@ -684,6 +684,24 @@ class Table(ABC):
         """
         raise NotImplementedError
 
+    def to_lance(self, **kwargs) -> lance.LanceDataset:
+        """Return the table as a lance.LanceDataset.
+
+        Returns
+        -------
+        lance.LanceDataset
+        """
+        raise NotImplementedError
+
+    def to_polars(self, **kwargs) -> "pl.DataFrame":
+        """Return the table as a polars.DataFrame.
+
+        Returns
+        -------
+        polars.DataFrame
+        """
+        raise NotImplementedError
+
     def create_index(
         self,
         metric="l2",