Fix sphere() functions to use explicit cast for WHPG compatibility

The sphere() SQL functions were defined as 'SELECT ROW($1, $2)' which
returns a generic record type. WHPG (Greenplum/PostgreSQL 12.12) is
stricter about type matching in SQL function bodies and requires the
return value to match the declared composite type exactly.

This caused runtime errors:
  ERROR: return type mismatch in function declared to return
sphere_vector
  DETAIL: Final statement returns record instead of vector at column 1.

Fix by adding explicit casts: 'SELECT ROW($1, $2)::sphere_vector'

Author: Ngalstyan4

src/sql/finalize.sql

@@ -189,16 +189,16 @@ CREATE OPERATOR @# (
 -- List of functions
 
 CREATE FUNCTION sphere(vector, real) RETURNS sphere_vector
-IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)';
+IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)::sphere_vector';
 
 CREATE FUNCTION sphere(halfvec, real) RETURNS sphere_halfvec
-IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)';
+IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)::sphere_halfvec';
 
 CREATE FUNCTION sphere(rabitq8, real) RETURNS sphere_rabitq8
-IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)';
+IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)::sphere_rabitq8';
 
 CREATE FUNCTION sphere(rabitq4, real) RETURNS sphere_rabitq4
-IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)';
+IMMUTABLE PARALLEL SAFE LANGUAGE sql AS 'SELECT ROW($1, $2)::sphere_rabitq4';
 
 CREATE FUNCTION quantize_to_rabitq8(vector) RETURNS rabitq8
 IMMUTABLE STRICT PARALLEL SAFE LANGUAGE c AS 'MODULE_PATHNAME', '_vchord_vector_quantize_to_rabitq8_wrapper';