propers: add August's collect and antiphon text

11 collects, 4 antiphons -- including backfilling the three pre-existing
August entries (Lawrence, Assumption, Augustine) now that the pulling
methodology exists. Also updates three pre-existing tests whose dates
collided with this month's new real content: the vigil-of-St.-Lawrence
backward-transfer case now runs into a real feast at its landing day
instead of an empty one (confirmed correct against the live reference
engine, including the surviving commemoration on the impeded Sunday
itself), and two other tests moved off Aug 9/10 to dates unaffected by
the new data.

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

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

@@ -0,0 +1,17 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617) — read
+# directly from the reference engine's own real-date output (2025-08-28).
+id: st-augustine-collect
+text:
+  la: |
+    Orémus.
+    Adésto supplicatiónibus nostris, omnípotens Deus: et, quibus fidúciam sperándæ pietátis indúlges, intercedénte beáto Augustíno Confessóre tuo atque Pontífice, consuétæ misericórdiæ tríbue benígnus efféctum.
+    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.
+    Graciously hear our supplications, O Almighty God, and as Thou hast given unto us the hope that we are of the number of them upon whom Thou wilt show mercy, grant unto us in thy goodness, that, helped by the prayers of thy blessed Confessor and Bishop Augustine, we may experience the fulfillment of thine accustomed loving-kindness.
+    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