Add the Circumcision of Our Lord (Jan 1) as a proper temporal feast

Jan 1 previously fell through to generic Christmastide-feria content with
no identity of its own, despite being Christmas's own Octave Day. Adds a
`fixed-date` anchor kind to calendar/movable-feasts.ts's MovableAnchor
(the existing easter/nth-sunday kinds can't express "always Jan 1"),
plus the feast's collect, Magnificat/Benedictus antiphons, full Lauds
psalmody, capitulum, versicle, and two Matins nocturn readings (Leo the
Great, Ambrose), sourced from Sancti/01-01.txt.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014axryJBrRswYh2niA7WCUc

src/data/propers/common/lauds-capitulum-circumcision.yml

@@ -0,0 +1,16 @@
+# Read from web/www/horas/Latin/Sancti/01-01.txt's own [Capitulum Laudes]
+# and its English counterpart. Also serves Vespers (see
+# hours/vespers.ts's vespersCapitulumForOverride: no distinct
+# `vespers-capitulum-circumcision` file exists in the source either — the
+# reference engine reuses this same chapter at both hours, same pattern
+# already established for every other feast this project has authored).
+id: lauds-capitulum-circumcision
+text:
+  la: "Fratres: Appáruit grátia Dei Salvatóris nostri ómnibus homínibus, erúdiens nos, ut abnegántes impietátem, et sæculária desidéria, sóbrie, et juste, et pie vivámus in hoc sǽculo."
+  en: "Brethren: The grace of God that bringeth salvation hath appeared to all men, teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly in this present world."
+citation:
+  la: "Tit 2:11-12"
+  en: "Tit 2:11-12"
+status:
+  la: verified
+  en: verified