Isso retorna o resultado desejado com os dados de amostra. Não tenho certeza se funcionará para dados do mundo real:
select k,
min(v) over (partition by group_nr) as min_v,
max(v) over (partition by group_nr) as max_v
from (
select *,
sum(group_flag) over (order by v,k) as group_nr
from (
select *,
case
when lag(k) over (order by v) = k then null
else 1
end as group_flag
from window_test
) t1
) t2
order by min_v;
Deixei de fora o
DISTINCT no entanto. 
