_YEAR_PERIODS ('год') → month=1 collided with Q1 ('I квартал') → month=1
for the same region/year: both produced obs_date=YYYY-01-01, so the second
series in the XML silently overwrote the first in the in-memory by_key dict.
Fix: add _emiss_period_granularity() and extend the dedup key from
(region, obs_date) to (region, obs_date, granularity). 'year' and 'quarter'
are now distinct slots, so both rows survive the parser and reach the upsert.
Test: test_yearly_and_q1_both_survive_dedup verifies len==2 with both
values present; test_period_granularity covers all classification branches.
