Generalize non-Sunday movable feasts into one Easter-offset resolver

The bespoke applyImmaculateHeart function (following the applyMarianSaturday/
applyChristTheKing precedent of one hand-written override function per
feast) doesn't scale: several more feasts are planned that all reduce to
"weekday N days from Easter Sunday" (Ember/Rogation days, more
Sacred-Heart-family Marian devotions, St. Joseph's pre-1955 Eastertide
feast, Lenten Friday Passion devotions), and one-off functions invite
subtle ordering bugs -- applyImmaculateHeart had to be sequenced after
applyMarianSaturday specifically or it would have been silently clobbered.

Replaced with calendar/movable-feasts.ts's generic applyMovableFeasts,
which scans calendar/temporal-feasts.ts's existing per-feast YAML records
for a new optional `easterOffset` field. Adding the next movable feast is
now a new data/calendar/temporal-feasts/<id>.yml file with `rank` and
`easterOffset` set, not a new TypeScript function. Same rank-compared,
commemorate-the-loser semantics as before, just centralized instead of
duplicated per feast.

christ-the-king, marian-saturday, and christmas-octave-sunday stay as
their own functions -- they're structurally different rules (a fixed
month-position search, a date-less fallback default, and a fixed-date-
range Sunday search, respectively), not Easter offsets, so force-fitting
them into this table wouldn't actually simplify anything.

No behavior change -- the existing Immaculate Heart of Mary test suite
passes unchanged through the new generic path.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VZSAgRi4QE4XRTqVto93zA

src/calendar/index.ts

@@ -8,6 +8,7 @@ import { resolveCollision } from './collision';
 import { addDays, toIsoDate } from './date-math';
 import { easterSunday } from './easter';
 import { activeOctavesFor, strictestThreshold } from './octaves';
+import { applyMovableFeasts } from './movable-feasts';
 
 /**
  * A day's occurrence considered on its own — no awareness of what an
@@ -105,7 +106,7 @@ export function resolveDay(isoDate: string): LiturgicalDay {
   winner = applyMarianSaturday(isoDate, weekday, temporalCategory, winner, commemorations);
   winner = applyChristTheKing(isoDate, winner, commemorations);
   winner = applyChristmasOctaveSunday(isoDate, weekday, winner, commemorations);
-  winner = applyImmaculateHeart(isoDate, winner, commemorations);
+  winner = applyMovableFeasts(isoDate, winner, commemorations);
   applyEpiphany6Commemoration(isoDate, commemorations);
 
   return { date: isoDate, weekday, season, temporalCategory, winner, commemorations };
@@ -245,54 +246,6 @@ function applyChristmasOctaveSunday(
   return winner;
 }
 
-/**
- * User decision, 2026-08-22: relocated off the fixed Aug 22 date (which
- * collided outright with the Assumption's own octave-closing day —
- * Pius XII's 1944 decree fixed it there, but this project keeps the
- * older Tridentine "Octave Day of the Assumption" too) to the *other*
- * well-documented historical assignment: the Saturday after the Feast
- * of the Sacred Heart. Real history (not a guess): this was the
- * feast's actual diocesan date from 1914 until the 1944 fixed-date
- * decree, and is also the date Paul VI's 1969 reform returned to — so
- * it has continuity on both sides of the Aug-22 interlude, unlike
- * inventing a "Saturday after the octave of Sacred Heart" pattern (no
- * such rule was ever real; Sacred Heart itself doesn't even have an
- * octave modeled in this codebase). Sacred Heart is Easter+68 (always
- * a Friday, see data/calendar/easter-offsets.yml's own derivation
- * comment) — this is the very next day, Easter+69.
- *
- * Runs last, after applyMarianSaturday, deliberately: Easter+69 is
- * always a Saturday, so absent this override the day would otherwise
- * just fall to the generic "Our Lady's Saturday" default — a specific
- * named Marian feast should always supersede that generic filler, not
- * lose to whichever ran first. Any temporal winner reaching here
- * (marian-saturday or a plain post-Pentecost Sunday-of-the-week id)
- * has no real standing of its own and is simply superseded, same as
- * applyChristTheKing's unconditional-when-temporal branch. Rank
- * compared via compareFeastClass, same as every other override in this
- * file — a duplex-2-classis feast displaces anything weaker, but a
- * higher-ranked sanctoral saint who happens to land on the same
- * Saturday keeps the day and Immaculate Heart is commemorated instead.
- */
-function applyImmaculateHeart(isoDate: string, winner: DayWinner, commemorations: Commemoration[]): DayWinner {
-  const year = Number(isoDate.slice(0, 4));
-  const targetDate = addDays(toIsoDate(easterSunday(year)), 69);
-  if (isoDate !== targetDate) {
-    return winner;
-  }
-  const IMMACULATE_HEART: DayWinner = { kind: 'temporal', id: 'immaculate-heart-of-mary' };
-  if (winner.kind === 'temporal') {
-    commemorations.push({ kind: 'temporal', id: winner.id });
-    return IMMACULATE_HEART;
-  }
-  if (compareFeastClass(winner.rank, 'duplex-2-classis') >= 0) {
-    commemorations.push({ kind: 'temporal', id: 'immaculate-heart-of-mary' });
-    return winner;
-  }
-  commemorations.push({ kind: 'sanctoral', id: winner.id, name: winner.name, rank: winner.rank });
-  return IMMACULATE_HEART;
-}
-
 /**
  * Layered on top of everything above, same spirit as applyOctaves: never
  * changes decideOccurrence's own rules, just relabels the result on a free