calendar: pull September's sanctoral calendar (pre-1955 pull, 9/12)

14 saints (12 real winners + 2 stubs), plus a propers-slug update for the
pre-existing Nativity of the BVM entry. Two monastic-calendar-specific
finds: St. Nicholas of Tolentino (Sep 10) overrides what the base
Tridentine table treats as a plain Nativity-octave continuation, and St.
Januarius (Sep 19) is a monastic-only addition absent from the base table
entirely. Also flags (not yet acted on) that the pre-existing Sep 29 St.
Michael mapping doesn't appear to hold in this pull's actual target
track -- see the sanctoral-calendar.yml comment for detail.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/data/calendar/saints/nativity-bvm.yml

@@ -1,7 +1,10 @@
 # Verified against Divinum Officium (web/www/horas/Latin/Sancti/09-08.txt,
-# untagged/default [Rank] block).
+# untagged/default [Rank] block). Propers backfilled during the September
+# pull (live kalendar/prayTertia check, 2025-09-08) now that the
+# collect-pulling methodology exists -- own proper collect and antiphon;
+# wins outright over the stub St. Hadrian (see st-hadrian.yml).
 id: nativity-bvm
 name: "The Nativity of the Blessed Virgin Mary"
 rank: duplex-2-classis
 common: common-of-the-bvm
-propers: null
+propers: "nativity-bvm"