Add plural common-of-apostles Matins hymn/invitatory files

The Octave Day of Ss. Peter and Paul (Jul 6) uses common:
common-of-apostles (the plural id, distinct from the singular
common-of-an-apostle most single-apostle feasts use), but no
matins-hymn-common-of-apostles.yml or matins-invitatory-common-of-
apostles.yml existed, so it fell through to the plain ferial default for
both. Duplicated the singular Common's identical source text under the
plural id, matching the existing convention already used for that
Common's Lauds hymn/capitulum/responsory/versicle files.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LGsATZvfnpQ81HQuoF5JuL

src/data/propers/common/matins-hymn-common-of-apostles.yml

@@ -0,0 +1,101 @@
+# Same source text as matins-hymn-common-of-an-apostle.yml (Commune/
+# C1.txt's own [Hymnus Matutinum] is identical whether one or several
+# apostles are being commemorated) -- duplicated under the plural id
+# because `common: common-of-apostles` (distinct from `common-of-an-
+# apostle`, see calendar/feasts.ts's SaintRecord.common) is what
+# octave-of-ss-peter-and-paul.yml actually carries, mirroring the
+# existing lauds-hymn/capitulum/responsory/versicle-common-of-apostles
+# duplicate-under-plural-id convention.
+id: matins-hymn-common-of-apostles
+text:
+  la: >-
+    Ætérna Christi múnera,
+
+    Apostolórum glóriam,
+
+    Palmas et hymnos débitos
+
+    Lætis canámus méntibus.
+
+
+    Ecclesiárum Príncipes,
+
+    Belli triumpháles duces,
+
+    Cæléstis aulæ mílites,
+
+    Et vera mundi lúmina.
+
+
+    Devóta Sanctórum fides,
+
+    Invícta spes credéntium,
+
+    Perfécta Christi cáritas
+
+    Mundi tyránnum cónterit.
+
+
+    In his Patérna glória,
+
+    In his triúmphat Fílius,
+
+    In his volúntas Spíritus,
+
+    Cælum replétur gáudio.
+
+
+    Patri, simúlque Fílio,
+
+    Tibíque Sancte Spíritus,
+
+    Sicut fuit, sit júgiter
+
+    Sæclum per omne glória. Amen.
+  en: >-
+    Th' eternal gifts of Christ the King,
+
+    The Apostles' glory, let us sing;
+
+    And all with hearts of gladness raise
+
+    Due hymns of thankful love and praise.
+
+
+    For they the Church's princes are,
+
+    Triumphant leaders in the war,
+
+    The heavenly King's own warrior band,
+
+    True lights to lighten every land.
+
+
+    Theirs was the steadfast faith of saints,
+
+    The hope that never yields nor faints,
+
+    The love of Christ in perfect glow,
+
+    That lay the prince of this world low.
+
+
+    In them the Father's glory shone,
+
+    In them the Spirit's will was done,
+
+    The Son himself exults in them;
+
+    Joy fills the new Jerusalem.
+
+
+    Praise to the Father, with the Son,
+
+    And Holy Spirit, Three in One;
+
+    As ever was in ages past,
+
+    And so shall be while ages last. Amen.
+status:
+  la: verified
+  en: verified