Fix Vespers concurrentia to compare today's rank against tomorrow's directly

keepsOwnSecondVespers used a fixed duplex-2-classis floor on today's rank
alone, so a lower-ranked but still-real sanctoral winner (e.g. Simplex)
tomorrow could still steal First Vespers from a higher-ranked-but-below-the-
floor winner today (semiduplex St. Raymond Nonnatus losing to simplex St.
Giles on 2026-08-31). The real "De Concurrentia Officii" rubric compares the
two days' ranks directly, with ties going to tomorrow — replace the floor
with that comparison when both sides have a real sanctoral winner, keeping
the floor only as a fallback against a plain Sunday.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014QEe9oTbn1UjQVAYcCoW1a

tests/calendar/vespers.test.ts

@@ -90,4 +90,29 @@ describe('resolveEveningDay', () => {
     expect(day.date).toBe('2026-08-24');
     expect(day.commemorations).toContainEqual(expect.objectContaining({ kind: 'sanctoral', id: 'st-louis' }));
   });
+
+  it('a higher-ranked today keeps its own Second Vespers against a lower-ranked tomorrow, even below the old duplex-2-classis floor', () => {
+    // Aug 31, 2026: St. Raymond Nonnatus (Semiduplex) vs. Sep 1's St. Giles
+    // (Simplex). Raymond outranks Giles, so Raymond should keep his own
+    // evening even though Semiduplex never cleared the old fixed
+    // duplex-2-classis floor -- the real "De Concurrentia Officii" rule is a
+    // direct comparison against tomorrow's rank, not a fixed threshold on
+    // today alone. Reported by the user 2026-08-31.
+    const day = resolveEveningDay('2026-08-31');
+    expect(day.date).toBe('2026-08-31');
+    expect(day.winner).toMatchObject({ kind: 'sanctoral', id: 'st-raymond-nonnatus' });
+    expect(day.commemorations).toContainEqual(expect.objectContaining({ kind: 'sanctoral', id: 'st-giles', vespersNote: 'tomorrow' }));
+  });
+
+  it('an exact rank tie goes to tomorrow, per the rubric\'s tie-break', () => {
+    // Aug 25, 2026: St. Louis (Simplex) vs. Aug 26's St. Zephyrinus (also
+    // Simplex) -- live-verified (see hasFirstVespers's own doc comment):
+    // "Vespera de sequenti; nihil de præcedenti." Tomorrow wins on the tie,
+    // and Louis (Simplex) is excluded from commemoration, same as any other
+    // Simplex predecessor.
+    const day = resolveEveningDay('2026-08-25');
+    expect(day.date).toBe('2026-08-26');
+    expect(day.winner).toMatchObject({ kind: 'sanctoral', id: 'st-zephyrinus' });
+    expect(day.commemorations.some((c) => c.kind === 'sanctoral' && c.id === 'st-louis')).toBe(false);
+  });
 });