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/ss-cornelius-and-cyprian.yml

@@ -0,0 +1,13 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), live
+# kalendar check (2025-09-16, 2026-09-16) -- winner outright, Semiduplex,
+# over the stub Ss. Euphemia, Lucy, and Geminianus (see
+# ss-euphemia-lucia-and-geminianus.yml). In years where Sep 16 itself
+# falls on the movable September Ember Wednesday, that Ember day is
+# commemorated instead of Euphemia et al. (confirmed 2026) -- doesn't
+# change this saint's own outright win either way. No unique collect: the
+# raw file at this MM-DD slot (Sancti/09-16.txt) is empty.
+id: ss-cornelius-and-cyprian
+name: "Ss. Cornelius, Pope, and Cyprian, Bishop, Martyrs"
+rank: semiduplex
+common: common-of-several-martyrs
+propers: null