calendar: real occurrence/precedence resolution (feast ranks, sanctoral content)

Replaces the FeastRank placeholder with a real ordered FeastClass (the old
pre-1955 six-level scale) and a new TemporalCategory (privileged/ordinary
Sunday/feria). calendar/commemorations.ts's decideOccurrence encodes the
actual precedence rules as explicit, commented branches per category
rather than the reference engine's own opaque numeric weights — this app
targets one ruleset, so the readability trade-off is worth it. Category
membership (data/calendar/temporal-categories.yml) is a best-effort
reconstruction of the pre-1955 tradition, not sourced from a primary text;
expect corrections.

calendar/feasts.ts resolves real sanctoral candidates, and resolveDay()
wires it all together — occurring/temporalCategory are no longer stubs.
isDoubleOrHigher (hours/antiphon.ts) is now a real comparison instead of
a hardcoded false.

Seeded 7 real saints/feasts, each verified directly against Divinum
Officium's own rank data (not reconstructed from memory) as a small,
growable start: St. Lawrence, the Assumption, St. Augustine, the Nativity
of the BVM, St. Michael, All Saints, the Immaculate Conception.

src/hours/antiphon.ts

@@ -1,4 +1,5 @@
 import type { OccurringFeast } from '../calendar/types';
+import { isAtLeast } from '../calendar/commemorations';
 
 export interface SplitAntiphon {
   incipit: string;
@@ -30,13 +31,13 @@ export function splitAntiphon(text: string): SplitAntiphon {
  * said before the psalms (the full text is always said after, regardless
  * of rank).
  *
- * FeastRank is an open string with no defined hierarchy yet (see
- * calendar/types.ts), and `occurring` is always [] until milestone 4 wires
- * up real feast data — so this can only ever return false today. That's
- * the *correct* answer for every day currently reachable (a plain ferial
- * day is below Double), not a stub papering over missing logic; it starts
- * doing real work the moment FeastRank has an ordering to compare against.
+ * Only asks whether the day's *winning* feast (not a merely-commemorated
+ * one) is Double-or-higher — a privileged Sunday with nothing occurring,
+ * or a commemorated low-rank saint, both correctly return false here. A
+ * Sunday being "privileged" doesn't by itself make this true; that's a
+ * `TemporalCategory` question, not a `FeastClass` one.
  */
-export function isDoubleOrHigher(_occurring: OccurringFeast[]): boolean {
-  return false;
+export function isDoubleOrHigher(occurring: OccurringFeast[]): boolean {
+  const winner = occurring.find((feast) => !feast.commemorated);
+  return winner ? isAtLeast(winner.rank, 'duplex') : false;
 }