Rename _to_matrix to _ensure_matrix

Rename helper function _to_matrix to _ensure_matrix and update its call site in ExprLike ufunc handling. The change preserves behavior (numpy arrays are viewed as MatrixExpr/MatrixGenExpr and other Expr instances map to MatrixExpr/MatrixGenExpr) while clarifying the function's intention.

Author: Zeroto521

src/pyscipopt/expr.pxi

@@ -251,7 +251,7 @@ cdef class ExprLike:
                     return NotImplemented
                 # If the np.ndarray is of numeric type, all arguments are converted to
                 # MatrixExpr or MatrixGenExpr and then the ufunc is applied.
-                return ufunc(*[_to_matrix(a) for a in args], **kwargs)
+                return ufunc(*[_ensure_matrix(a) for a in args], **kwargs)
 
             if ufunc is np.add:
                 return args[0] + args[1]
@@ -1056,7 +1056,7 @@ cdef inline object _wrap_ufunc(object x, object ufunc):
         return res.view(MatrixGenExpr) if isinstance(res, np.ndarray) else res
     return ufunc(_to_const(x))
 
-cdef inline object _to_matrix(object arg):
+cdef inline object _ensure_matrix(object arg):
     if type(arg) is np.ndarray:
         return arg.view(MatrixExpr)
     matrix = MatrixExpr if isinstance(arg, Expr) else MatrixGenExpr