Fix ordinary-Sunday precedence and unify getDayLabel's commemoration rendering

Two related fixes surfaced while chasing why St. Gregory Thaumaturgus
appeared to be misdated on Nov 18:

- calendar/commemorations.ts's `ordinary-sunday` case was transferring a
  Semiduplex (or lower) saint off the Sunday instead of commemorating it
  in place — an earlier, unverified guess. Live-verified against both
  Tridentine 1906 and Divino Afflatu 1954 (St. Gregory Thaumaturgus, St.
  Clement, St. Apollinaris, St. Thomas Becket, all real cases): the saint
  stays and is commemorated on the Sunday itself, same as Simplex, never
  pushed to the next open day. This is what was actually moving Gregory
  onto Nov 18 — not a data error. `applyChristmasOctaveSunday`'s own
  Dec 26-29 special case needed a matching adjustment (per its own
  documented intent, the displaced saint there is deliberately *not*
  commemorated in place, since he reappears in full on Dec 30 instead).

- getDayLabel had five branches, each hand-assembling its own
  filter/format logic for which commemorations to show — which is why
  the octave phrasing, the closing-day title, and a missing Sunday
  commemoration turned into three separate bugs earlier instead of one.
  Replaced with a single shared `collectCommemorations` used by every
  branch. This also exposed that the sanctoral-winner branch never
  showed any commemorated saint at all, and every other branch only
  showed the *first* one (`.find()`), silently dropping real collisions
  — both now show every commemorated saint, matching this app's own
  generous-commemoration design.

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

src/calendar/index.ts

@@ -197,6 +197,23 @@ function applyChristmasOctaveSunday(
   const day = Number(dayStr);
 
   if (day >= 26 && day <= 29 && weekday === 'sunday') {
+    // The displaced saint isn't commemorated in place (per this
+    // function's own doc comment, "he reappears in full on Dec 30
+    // instead") — strip the sanctoral commemoration `decideOccurrence`
+    // already pushed for him before this override ran, the same
+    // candidate the Dec 30 branch below will look up again to revive.
+    // Only became reachable once `commemorations.ts`'s `ordinary-sunday`
+    // case started commemorating Semiduplex/Simplex in place instead of
+    // transferring them (see its own doc comment) — before that fix, a
+    // `transfer` signal carried the candidate forward instead of a
+    // commemoration, so there was nothing here to strip.
+    const displaced = getSanctoralCandidatesFor(isoDate)[0];
+    if (displaced) {
+      const idx = commemorations.findIndex((c) => c.kind === 'sanctoral' && c.id === displaced.id);
+      if (idx !== -1) {
+        commemorations.splice(idx, 1);
+      }
+    }
     return { kind: 'temporal', id: 'christmas-octave-sunday' };
   }