Relocate Immaculate Heart of Mary off Aug 22 to Easter+69

Fixed Aug 22 collided outright with the Assumption's own octave-closing
day (both this project's blended calendar tracks are kept deliberately,
so one shouldn't permanently suppress the other). Moved IHM to the
Saturday after the Feast of the Sacred Heart -- its real diocesan date
from 1914 until Pius XII's 1944 fixed-date decree, and also the date the
1969 reform returned to.

Required real new mechanism, not just a data move: a new bespoke
calendar/index.ts override (applyImmaculateHeart, following the existing
applyMarianSaturday/applyChristTheKing precedent), a move from the
sanctoral saints store to the temporal-feasts store (different propers
lookup entirely), and a real bug fix in matins.ts's nocturnReadingIds,
which only ever picked up a *sanctoral* winner's own reading file.

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

src/hours/resolve-common.ts

@@ -35,7 +35,12 @@ export function resolveCommon(id: string): ResolvedText {
 // override-eligible — see hours/lauds.ts's getPsalmodyOverrideFor, which
 // shares this set (imported from here, not duplicated) since it's the
 // same "does this temporal identity carry its own real office" question.
-export const ALWAYS_OVERRIDE_TEMPORAL_IDS = new Set(['marian-saturday', 'christ-the-king', 'christmas-octave-sunday']);
+export const ALWAYS_OVERRIDE_TEMPORAL_IDS = new Set([
+  'marian-saturday',
+  'christ-the-king',
+  'christmas-octave-sunday',
+  'immaculate-heart-of-mary',
+]);
 
 /**
  * Which identity's own propers actually supply the office's content