Add metadata enums import and AGGREGATE function type to catalog interface

- Import FunctionStability, NullHandling, OrderPreservation, OrderDependence,
  and DistinctDependence enums from vgi.metadata for use in FunctionInfo
- Add AGGREGATE value to FunctionType enum for future aggregate function support
- Re-export imported enums via __all__ for convenient access

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: rustyconover

vgi/catalog/catalog_interface.py

@@ -13,6 +13,22 @@
 import pyarrow as pa
 
 import vgi.ipc_utils
+from vgi.metadata import (
+    DistinctDependence,
+    FunctionStability,
+    NullHandling,
+    OrderDependence,
+    OrderPreservation,
+)
+
+__all__ = [
+    # Re-exported from vgi.metadata
+    "DistinctDependence",
+    "FunctionStability",
+    "NullHandling",
+    "OrderDependence",
+    "OrderPreservation",
+]
 
 # Type aliases for improved code clarity and type checking.
 # At runtime, these are equivalent to their underlying types.
@@ -300,6 +316,7 @@ class FunctionType(Enum):
 
     SCALAR = "scalar"
     TABLE = "table"
+    AGGREGATE = "aggregate"
 
 
 class OnConflict(Enum):