Historically a floating Sunday (Jan 2-5, fixed to Jan 2 when no Sunday
falls there); per direct instruction this is instead fixed to Jan 2
every year for simplicity. Adds the feast's collect, Magnificat/
Benedictus antiphons, full Lauds psalmody, capitulum, the three-part
"Jesu dulcis memoria" hymn cycle (Vespers/Matins/Lauds), the Invitatory
antiphon, versicles, and two Matins nocturn readings (both St. Bernard
of Clairvaux), sourced from Tempora/Nat2-0.txt. Reuses the `fixed-date`
anchor kind added in the prior commit.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014axryJBrRswYh2niA7WCUc
