propers: add June's collect and antiphon text

Real collect text for all 16 June saints that have one, plus a real
antiphon for 4 of them and a fifth (Ss. Peter and Paul) that deliberately
reuses the Chair-of-Peter-at-Antioch antiphon text, matching the source's
own cross-reference — same extraction method as prior months.

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

src/data/propers/common/ss-marcellinus-peter-and-erasmus-collect.yml

@@ -0,0 +1,18 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617) — read
+# directly from the reference engine's own real-date output (2026-06-02).
+# Same convention as data/propers/temporal/*-collect.yml.
+id: ss-marcellinus-peter-and-erasmus-collect
+text:
+  la: |
+    Orémus.
+    Deus, qui nos ánnua beatórum Mártyrum tuórum Marcellíni, Petri atque Erásmi solemnitáte lætíficas: præsta, quǽsumus; ut, quorum gaudémus méritis, accendámur exémplis.
+    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.
+    O God, Who dost every year gladden us by the solemn memorial of your blessed Martyrs Marcellinus, Peter, and Erasmus, grant us grace, we beseech thee, not only to rejoice because of their worthy deeds, but also to tread in their footsteps.
+    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