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-euphemia-lucia-and-geminianus.yml

@@ -0,0 +1,15 @@
+# Genuinely unwinnable stub (verified 2025-09-16, a non-Ember year) --
+# always commemorated under Ss. Cornelius and Cyprian (see
+# ss-cornelius-and-cyprian.yml), never wins outright; both are fixed,
+# non-movable dates, so this isn't an artifact of the tested year. In
+# years where Sep 16 lands on the movable September Ember Wednesday
+# instead (confirmed 2026), this saint doesn't even surface as a
+# commemoration at all -- the Ember day takes that slot -- but that's a
+# separate, already-modeled temporal interaction (privileged-feria),
+# not a change to this saint's own standing. rank/propers unverified
+# placeholders.
+id: ss-euphemia-lucia-and-geminianus
+name: "Ss. Euphemia, Lucy, and Geminianus, Martyrs"
+rank: simplex
+common: common-of-several-martyrs
+propers: null