fix: propagate cast errors in add() (#3075)

When we write data with `add()`, we can input data to the table's
schema. However, we were using "safe" mode, which propagates errors as
nulls. For example, if you pass `u64::max` into a field that is a `u32`,
it will just write null instead of giving overflow error. Now it
propagates the overflow. This is the same behavior as other systems like
DuckDB.

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

python/python/tests/test_table.py

@@ -326,6 +326,24 @@ def test_add_struct(mem_db: DBConnection):
     table = mem_db.create_table("test2", schema=schema)
     table.add(data)
 
+    struct_type = pa.struct(
+        [
+            ("b", pa.int64()),
+            ("a", pa.int64()),
+        ]
+    )
+    expected = pa.table(
+        {
+            "s_list": [
+                [
+                    pa.scalar({"b": 1, "a": 2}, type=struct_type),
+                    pa.scalar({"b": 4, "a": None}, type=struct_type),
+                ]
+            ],
+        }
+    )
+    assert table.to_arrow() == expected
+
 
 def test_add_subschema(mem_db: DBConnection):
     schema = pa.schema(