calendar: pull January's sanctoral calendar (pre-1955 pull, 1/12)

20 saints for January, verified per-day against Divinum Officium (Monastic
Tridentinum 1617): 13 that actually win their day outright (rank pulled
from a live per-date query, since the static 1570/M1617 calendar text
files turned out unreliable once monastic-specific overrides apply) and
7 stubs for saints that only ever get commemorated, with an explicitly
flagged, unverified simplex rank guess pending correction.

Deliberately out of scope: pure octave-continuation days (In Octava S.
Stephani, the Epiphany-octave ferias) and fixed-date feasts of the
Lord/BMV (Circumcision, Epiphany) — sanctoral only, not temporal.

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

src/data/calendar/saints/st-marcellus-i.yml

@@ -0,0 +1,10 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), live kalendar
+# check (2029-01-16, no Sunday collision) -- winner outright, Semiduplex. Own
+# proper collect (web/www/horas/Latin/Sancti/01-16.txt's [Oratio]) -- see
+# propers/common/st-marcellus-i-collect.yml -- but no unique antiphon of his
+# own (Terce/Sext/None's antiphon there is the generic Common one).
+id: st-marcellus-i
+name: "St. Marcellus I, Pope and Martyr"
+rank: semiduplex
+common: common-of-a-martyr-bishop
+propers: "st-marcellus-i"