Add nameLa mechanism for bilingual header, proof set of 11 feasts + St. Lawrence

Threads an optional nameLa field through SanctoralIdentity/SaintRecord/
TemporalFeastRecord/ActiveOctave so day-label.ts can render real Latin
proper names instead of always falling back to English. Authors the
proof set: all 11 named temporal feasts plus St. Lawrence (chosen to
exercise the octave-headline and octave-commemoration code paths too).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwsZQMjALCvy7u9tFDWmuQ

src/data/calendar/temporal-feasts/christmas-day.yml

@@ -12,6 +12,10 @@
 # specifically.
 id: christmas-day
 name: "Christmas"
+# Nominative form of the reference engine's own title ("In Nativitate
+# Domini", Sancti/12-25.txt's [Rank]), matching this app's own
+# nominative-noun-phrase naming convention.
+nameLa: "Nativitas Domini"
 rank: duplex-1-classis
 octave:
   enabled: true