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-peter-ad-vincula-antiphon.yml

@@ -0,0 +1,12 @@
+# Verified against Divinum Officium (Latin/English Sancti/08-01.txt's own
+# [Ant 1] — a deliberate cross-reference to the Chair-of-Peter-at-Antioch
+# antiphon (Feb 22, see chair-of-st-peter-at-antioch-antiphon.yml), same
+# reuse pattern as Ss. Peter and Paul in June. Duplicated content, not a
+# shared reference, matching this project's one-file-per-id convention.
+id: st-peter-ad-vincula-antiphon
+text:
+  la: "Tu es pastor óvium, * Princeps Apostolórum, tibi tráditæ sunt claves regni cælórum."
+  en: "Thou art the Shepherd * of the sheep, and the Prince of the Apostles, and unto thee are given the keys of the kingdom of heaven."
+status:
+  la: verified
+  en: verified