calendar: model octaves as a generic, data-driven mechanism

Adds calendar/octaves.ts: a lookback over the past week collecting every
octave (sanctoral or temporal) still active on a date, stacking multiple
at once (Christmas + St. Stephen + St. John + Holy Innocents all
commemorated together within the Christmas Octave). Declared via an
optional `octave` field on a saint's own record or a new small
TemporalFeastRecord (calendar/temporal-feasts.ts) for temporal ids like
Christmas/Pentecost that didn't have a metadata record before -- data-
driven per user design discussion, with `{ enabled: true }` alone using
sensible defaults (8 days, semiduplex threshold) so a minimal declaration
works without authored content.

Wired into resolveDay as a post-processing layer: doesn't change how a
single day's own precedence contest is decided, just adds commemorations
for active octaves and occasionally overrides the winner when the
occurring saint doesn't clear the strictest active octave's threshold.

Populated so far: St. Lawrence's own octave (the one that repeatedly cost
real saints their spot in August), the three Comites Christi octaves
(Stephen/John/Innocents -- Thomas of Canterbury deliberately excluded,
per discussion), and Pentecost's (duplex threshold, user-specified).
Pentecost's octave offsets are also removed from temporal-categories.yml's
privileged-feria-major classification, letting a real candidate reach the
new octave layer instead of being transferred away first -- with the
side effect that Pentecost's own Ember Saturday no longer forces a
transfer (a sub-threshold saint is now commemorated in place instead, see
tests/calendar/transfer.test.ts's updated case). Assumption, Nativity
BVM, Immaculate Conception, and All Saints' own octaves are not yet
populated with octave data -- deliberately deferred to a follow-up pass.

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

src/calendar/types.ts

@@ -106,6 +106,34 @@ export interface SanctoralIdentity {
   rank: FeastClass;
 }
 
+/**
+ * Attached to a saint's own record (calendar/feasts.ts's SaintRecord) or a
+ * temporal feast's (calendar/temporal-feasts.ts's TemporalFeastRecord) to
+ * declare that it carries an octave — commemorated daily for `days` days
+ * after its own feast, layered on top of whatever normally wins each of
+ * those days. `enabled: false` (or the field simply absent) means no
+ * octave; `{ enabled: true }` alone is valid and uses every default below,
+ * satisfying the "turned on but no octave data authored yet" case —
+ * calendar/octaves.ts is the "generic way to commemorate an octave" that
+ * makes that minimal declaration meaningful on its own.
+ */
+export interface OctaveConfig {
+  enabled: boolean;
+  /** Length of the octave in days, inclusive of the feast's own day. Default 8. */
+  days?: number;
+  /** Rank threshold: an occurring saint at this rank or higher keeps the
+   * day for itself (the octave is merely commemorated back); below it, the
+   * octave wins the day instead and the saint is commemorated. Default
+   * 'semiduplex' — i.e. only a Simplex loses to the octave — matching
+   * every octave checked so far except Pentecost's (see
+   * data/calendar/temporal-feasts/pentecost-sunday.yml), which is
+   * stricter (`duplex`). */
+  wins?: FeastClass;
+  /** Matins reading proper id, if one has been sourced. Absent by default
+   * — most octaves checked so far have none. */
+  readingId?: string;
+}
+
 export type DayWinner =
   | { kind: 'temporal'; id: string }
   | ({
@@ -119,12 +147,15 @@ export type DayWinner =
 /**
  * A day can have more than one of these at once (a transferred feast can
  * displace a native saint who then also gets commemorated, alongside the
- * Sunday whose own occurrence pushed the transfer in the first place) —
- * hence a list, not a single flag. Extensible on purpose: a future
- * `{ kind: 'octave'; id: string }` variant joins this union once octaves
- * are modeled, without changing the shape callers already rely on.
+ * Sunday whose own occurrence pushed the transfer in the first place, or —
+ * since octaves were modeled — several overlapping octaves stacking on one
+ * date, e.g. Christmas + St. Stephen + St. John all commemorated together
+ * within the Christmas Octave) — hence a list, not a single flag.
  */
-export type Commemoration = { kind: 'temporal'; id: string } | ({ kind: 'sanctoral' } & SanctoralIdentity);
+export type Commemoration =
+  | { kind: 'temporal'; id: string }
+  | ({ kind: 'sanctoral' } & SanctoralIdentity)
+  | { kind: 'octave'; id: string; name: string };
 
 export interface LiturgicalDay {
   /** ISO date, e.g. "2026-08-09" */