Adds optional 'year' argument (defaults to most recent observed year for the target). Filters and ranks candidates by gov_population_yearly.population at that year. Returned column renamed population_acs -> population. Cohort year attached as attr(x, 'cohort_year'). Adds .resolve_cohort_year() helper. Updates test assertions to use 'population' column name. Regenerates man/cog_find_peers.Rd.