Revert ordinary-Sunday Semiduplex to transferring, per direct instruction

Keeps Simplex commemorating in place, but a Semiduplex feast on an
ordinary Sunday goes back to transferring off to the next open day —
this app's own design choice, not a correction against a reference
engine. The transfer mechanism is already generic: this file's `decideOccurrence`
only signals "couldn't hold onto this candidate" for the day itself;
calendar/index.ts's resolveDay is what independently checks each
neighboring day's own native occurrence for an incoming transfer and
claims it — no separate lookback logic needed.

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

tests/calendar/commemorations.test.ts

@@ -122,16 +122,16 @@ describe('decideOccurrence — ordinary-sunday', () => {
     expect(result.transfer).toBeUndefined();
   });
 
-  it('semiduplex stays and is commemorated, not transferred', () => {
-    // Live-verified (both Tridentine 1906 and Divino Afflatu 1954): St.
-    // Gregory Thaumaturgus (Semiduplex) lands on the 6th Sunday after
-    // Epiphany and is commemorated right there, not pushed to the next
-    // open day — same treatment as Simplex above, not a separate
-    // "too important to merely commemorate" tier.
+  it('semiduplex gets nothing here — transfers forward', () => {
+    // Per direct instruction: a Semiduplex feast on an ordinary Sunday is
+    // pushed off to the next open day (typically the Monday right after)
+    // rather than merely commemorated — see decideOccurrence's own
+    // `ordinary-sunday` case for the two-part transfer mechanism this
+    // signal feeds into.
     const result = decideOccurrence('ordinary-sunday', 'post-epiphany-2', saint('semiduplex'));
     expect(result.winner).toEqual({ kind: 'temporal', id: 'post-epiphany-2' });
-    expect(result.commemorations).toEqual([{ kind: 'sanctoral', id: 'x', name: 'St. Ereden', rank: 'semiduplex' }]);
-    expect(result.transfer).toBeUndefined();
+    expect(result.commemorations).toEqual([]);
+    expect(result.transfer).toEqual({ candidate: saint('semiduplex'), direction: 'forward' });
   });
 
   it('vigil gets nothing here — transfers backward', () => {