propers: add September's collect and antiphon text

6 collects, 1 antiphon -- including backfilling the pre-existing Nativity
of the BVM entry now that the pulling methodology exists.

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

src/data/propers/common/st-matthew-collect.yml

@@ -0,0 +1,17 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617) — read
+# directly from the reference engine's own real-date output (2026-09-21).
+id: st-matthew-collect
+text:
+  la: |
+    Orémus.
+    Beáti Apóstoli et Evangelístæ Matthǽi, Dómine, précibus adjuvémur: ut, quod possibílitas nostra non óbtinet, ejus nobis intercessióne donétur.
+    Per Dóminum nostrum Jesum Christum, Fílium tuum: qui tecum vivit et regnat in unitáte Spíritus Sancti, Deus, per ómnia sǽcula sæculórum.
+    ℟. Amen.
+  en: |
+    Let us pray.
+    Help us, O Lord, by the prayers of thine holy Apostle and Evangelist Matthew, that what for ourselves we are not able to obtain, may be freely given us at his petition.
+    Through Jesus Christ, thy Son our Lord, Who liveth and reigneth with thee, in the unity of the Holy Ghost, God, world without end.
+    ℟. Amen.
+status:
+  la: verified
+  en: verified