docs: fix BENE_MSIS docs, add cohort column reference, correct MAX RX info

fix: correct LST_DIAG_CD docs, TAF subtype keys, RUCC grouping, ZIP sources - LST_DIAG_CD is not auto-created for MAX; must be constructed from DIAG_CD_* columns - TAF gather_bene_level_diag_ndc_codes() creates LST_DIAG_CD on base_diag_codes, not base - Fix RUCC grouping: codes 1-3 metro, 4-9 non-metro (not 1-7 metro) - Fix ZIP centroids source: SimpleMaps/GeoNames, not NBER

fix: correct TAF dict keys, PQI names, LST_DIAG_CD docs, and dependency info - Fix TAF dct_files keys: dx->base_diag_codes, ndc->line_ndc_codes, occr->occurrence_code - Fix pediatric PQI indicator names: TPQP14-TPQP15 -> TAPD14-TAPD18 - Add gather_bene_level_diag_ndc_codes() context for TAF Elixhauser examples - Mark distributed as required dependency (not optional) - Fix Glossary: excl_missing_dob/excl_duplicated column names, LST_DIAG_CD creation context

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