kernel: carry omitted celebrations on Liturgical_day.t, reason and all

Precedence.resolution already tracked what happened to every losing
candidate -- commemorated, deferred, or omitted with a reason -- but
Liturgical_day.t had nowhere for the deferred and omitted buckets to land,
so Calendar dropped them at the door. Task 12's no-celebration-lost
invariant needs to read that accounting off the day result itself, not
re-resolve every day to reconstruct it, so a reason recorded nowhere is not
recorded.

Add Liturgical_day.omitted : ('r Celebration.t * string) list, after
transferred_out and before citations. Calendar.resolve_day now folds
resolution.omitted (Precedence's own native omissions, reasons intact) and
resolution.deferred (mapped to "deferred: transfer placement not yet
implemented (Task 6)") into it.

Adds a full-day accounting test against the whole Calendar pipeline: four
colliding sanctoral entries plus the day's feria, checked as a slug set
(matching test_precedence.ml's own nothing-silently-lost test) so a
candidate silently dropped or duplicated into two buckets would fail it,
plus an identity check that the deferred and admission-limit reasons don't
get swapped.

1 files changed, 9 insertions, 4 deletions

diff --git a/lib/kernel/calendar.mli b/lib/kernel/calendar.mli
index 50ff8f8..2469f2a 100644
--- a/lib/kernel/calendar.mli
+++ b/lib/kernel/calendar.mli
@@ -9,10 +9,15 @@
 
     This module resolves each day's temporal-vs-sanctoral contest but does
     not yet place deferred transfers (RG 96-98): a losing candidate the
-    rite's rules send to [Precedence.Transfer] is absent from the result
-    entirely on this pass -- not observed, not commemorated, and
-    [transferred_in]/[transferred_out] both stay [None] everywhere. Task 6
-    adds the fixed-point placement pass that closes this gap. *)
+    rite's rules send to [Precedence.Transfer] is not observed and not
+    commemorated on the day it lost, and [transferred_in]/[transferred_out]
+    both stay [None] everywhere -- but it is not silently dropped either. It
+    lands in that day's [Liturgical_day.omitted] with the reason ["deferred:
+    transfer placement not yet implemented (Task 6)"], alongside
+    [Precedence]'s own native omissions (yielded to a higher day; admission
+    limit reached), each with its own reason. Task 6 adds the fixed-point
+    placement pass that actually places these; until then, this is the
+    day's complete, honest accounting of what happened to every candidate. *)
 
 (** [year rite layer y] resolves every day of the liturgical year that opens
     in civil year [y]: from [rite.year_start y] through the day before