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, 14 insertions, 7 deletions

diff --git a/lib/kernel/calendar.ml b/lib/kernel/calendar.ml
index fd23377..1cdd1fa 100644
--- a/lib/kernel/calendar.ml
+++ b/lib/kernel/calendar.ml
@@ -35,6 +35,15 @@ let year_bounds (rite : ('s, 'r) Rite.t) (y : int) : Date.t * Date.t =
   in
   (start, stop)
 
+(* [resolution.deferred] (RG 96-98 transfer candidates) has nowhere to be
+   PLACED yet -- Task 6 adds the fixed-point pass that does -- but it must
+   still be accounted for on the day it lost, not silently dropped: Task
+   12's no-celebration-lost invariant reads [Liturgical_day.omitted], so a
+   deferred candidate folds in there too, with its own reason distinct from
+   Precedence's native omissions ("omitted: yielded to a higher day",
+   "omitted: admission limit reached"). *)
+let deferred_reason = "deferred: transfer placement not yet implemented (Task 6)"
+
 (* RG 91's contest for one date: the temporal office against every sanctoral
    entry whose Date_spec resolves to it. [Layer.on_date] is keyed on exactly
    (month, day), which for a [Fixed] spec -- the only form Plan 2 ships -- is
@@ -53,13 +62,10 @@ let resolve_day (rite : ('s, 'r) Rite.t) (idx : 'r Layer.by_date) (date : Date.t
   in
   let ctx = { Precedence.date; season = temporal.Temporal.season; weekday = temporal.Temporal.weekday } in
   let resolution = Precedence.resolve rite.Rite.rules ctx ~temporal:temporal_candidate ~sanctoral in
-  (* [resolution.deferred] (RG 96-98 transfer candidates) and
-     [resolution.omitted] (yielded/admission-limit losers) have no field to
-     land in on Liturgical_day.t yet, so both are simply absent from today's
-     result -- deliberately incomplete for a deferred candidate, which is
-     thereby neither observed nor commemorated here, and not yet placed on
-     any later day either ("deferred: transfer placement not yet implemented
-     (Task 6)"). Task 6's fixed-point pass closes this gap. *)
+  let omitted =
+    List.map (fun (c, reason) -> (c.Precedence.cel, reason)) resolution.Precedence.omitted
+    @ List.map (fun c -> (c.Precedence.cel, deferred_reason)) resolution.Precedence.deferred
+  in
   {
     Liturgical_day.date;
     rite = rite.Rite.id;
@@ -69,6 +75,7 @@ let resolve_day (rite : ('s, 'r) Rite.t) (idx : 'r Layer.by_date) (date : Date.t
       List.map (fun (c, p) -> (c.Precedence.cel, p)) resolution.Precedence.commemorations;
     transferred_in = None;
     transferred_out = None;
+    omitted;
     citations = [];
   }