calendar: give Advent's ordinary ferias their own precedence tier

Found while starting the December sanctoral pull: Advent's plain
(non-Ember) weekday ferias have real standing in the live Monastic 1617
engine that the existing ordinary-feria category couldn't represent --
a Simplex saint (St. Bibiana, Dec 2) is merely commemorated there rather
than winning outright, while a Semiduplex+ saint (St. Nicholas, Dec 6)
wins with the feria itself commemorated back. Adds a third, weaker
privileged-feria-minor tier (Semiduplex+ threshold, vs. privileged-
feria's Duplex+) rather than reusing either existing tier, mirroring how
privileged-feria/privileged-feria-major were split in March. Lent's own
ordinary ferias likely share this property but are left as-is, unverified
this session.

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

src/calendar/vespers.ts

@@ -44,6 +44,7 @@ function hasFirstVespers(day: LiturgicalDay): boolean {
 function keepsOwnSecondVespers(day: LiturgicalDay): boolean {
   if (
     day.weekday === 'sunday' ||
+    day.temporalCategory === 'privileged-feria-minor' ||
     day.temporalCategory === 'privileged-feria' ||
     day.temporalCategory === 'privileged-feria-major' ||
     isMajorFixedFeastOfTheLord(day.date)