Merge branch 'ef-major-litanies': the Major Litanies, and a kernel bug

Builds the Major Litanies (RG 80, 81, 109(f)) -- an item deferred three
times, each time on a reason that did not survive contact. Two recorded
blockers were false (a kernel signature said to be missing already
carried what was needed; Easter Monday, said to be unmarkable, occurs
exactly 8417 times in 8417 years) and a displacement estimate of ~97.7%
of years measured at 4 years in 46.

8611 days change in four shapes, zero unclassified: the commemoration
appearing on ordinary 25 Aprils, displacing St Mark's own on the four
II-class Sundays RG 111(b) governs, and relocating to the following
Tuesday in the 194 years RG 80's transfer clause fires. No day outside
25/26/27 April differs at all, and observed, rank, colour, season, week
and transferred_in are byte-identical across all 3074246 days.

The entity is a Commemoration_only sanctoral entry, which honours RG 81
structurally rather than by special case: Precedence.resolve partitions
such candidates out of the band contest, so 'nihil fit in Officio' holds
by construction, and being sanctoral-origin it can never claim RG 113's
de-Tempore first place.

And it surfaced a latent kernel bug. Calendar.build_day decided whether
a transferred candidate had settled by testing only whether it became
that day's observed celebration -- correct for every prior use, a losing
feast that wins its unblocked target, and wrong for a Commemoration_only
candidate, which can never be observed by the same status that lets it
transfer. The first fix accepted two settlement channels and the review
found a third: a candidate capped out by admit at its target. That third
case was already visible inside the task's own mutation proof, as an
undiagnosed ninth failure it had set aside.

The fix is a provable no-op in isolation: a3afb19 plus the new
calendar.ml alone, swept over every day of the domain, is byte-identical
to base.

1 files changed, 134 insertions, 4 deletions

diff --git a/test/test_golden.ml b/test/test_golden.ml
index fdfc01d..7b461bf 100644
--- a/test/test_golden.ml
+++ b/test/test_golden.ml
@@ -173,7 +173,18 @@ let test_easter_extreme_1598 () =
 
 (* 1666: latest Gregorian Easter possible, 25 April -- hand-verified via
    Gauss's algorithm (a = 13, b = 16, c = 66, ..., h = 29, l = 5, m = 0 ->
-   25 April). Same citations as 1598 above. *)
+   25 April). Same citations as 1598 above.
+
+   ef-major-litanies task: 25 April = Easter Sunday is RG 80's own FIRST
+   trigger condition ("si vero eo die occurrit dominica Paschatis...
+   transferuntur in sequentem feriam III") -- this pin, already the
+   project's own hand-verified latest-Easter witness, now ALSO carries the
+   transfer this rule requires: [major-litanies] departs 25 April for
+   27 April (Easter+2, "the following Tuesday" -- Precedence_ef.transfer_
+   target's own Litanies branch has the full citation). Nothing else about
+   this day changes: [observed]/[comms]/[in] are exactly as before,
+   proving the Litanies departure is additive, not disruptive, to the
+   day Easter itself owns outright. *)
 let test_easter_extreme_1666 () =
   check ~msg:"1666-04-24 Holy Saturday: still Passiontide, violet (RG 128)" 1666 4 24
     "1666-04-24 saturday season=passiontide week=2 slug=ef-passiontide-2-saturday rank=class-1 colour=violet subject=lord \
@@ -181,7 +192,21 @@ let test_easter_extreme_1666 () =
   check ~msg:"1666-04-25 latest possible Easter (Gauss-verified): Paschaltide begins, white, class-1" 1666 4
     25
     "1666-04-25 sunday season=paschaltide week=1 slug=ef-easter-sunday rank=class-1 colour=white subject=temporal name_la=- comms=[] in=- \
-     out=[]"
+     out=[major-litanies->1666-04-27]";
+  (* The transfer's own target, positively pinned (not merely inferred from
+     [out] above): an ordinary Easter-octave Tuesday, I class, white (RG
+     119 -- white "a Missa Vigiliae paschalis usque ad Missam vigiliae
+     Pentecostis"), with the Litanies as its own sole, privileged
+     commemoration (RG 109(f); RG 111(a), "I class: none save one
+     privileged" -- {!PE.admit}'s own [Class1] case). No [transferred_in]
+     printed: [Liturgical_day.transferred_in] only ever names a candidate
+     that went on to WIN the day (calendar.ml's own [build_day]), and the
+     Litanies structurally never can (RG 81, Commemoration_only) -- this is
+     the SAME asymmetry {!Colitur_kernel.Calendar}'s own [settled_at] fix
+     (this task) exists to get right on the OTHER side of the ledger. *)
+  check ~msg:"1666-04-27 Easter+2: the Litanies' own transfer target, commemorated and privileged" 1666 4 27
+    "1666-04-27 tuesday season=paschaltide week=1 slug=ef-easter-1-tuesday rank=class-1 colour=white subject=temporal \
+     name_la=- comms=[major-litanies:privileged] in=- out=[]"
 
 (* 2038: the brief's "late modern case" -- Easter also 25 April (Gauss-
    verified: a = 5, b = 20, c = 38, ..., h = 29, l = 5, m = 0 -> 25 April,
@@ -203,13 +228,24 @@ let test_easter_extreme_1666 () =
    temporal-cycle-only test regardless (the two concerns -- Easter-extreme
    arithmetic and a sanctoral occurrence rule -- stay separate pins even
    though nothing forces that any more). *)
+(* ef-major-litanies task: 2038 is this file's own worked example for the
+   OTHER RG 80 trigger shape checked elsewhere in this task (Easter Monday
+   = 25 April, e.g. 2011) landing on the identical target (Easter+2) --
+   here Easter SUNDAY itself is 25 April, so the "following Tuesday" is
+   two days later, 27 April, not one; both shapes converge on Easter+2,
+   never on Easter+1 or Easter+3 (precedence_ef.ml's own [transfer_target]
+   Litanies branch has the full RG 80 citation and the arithmetic for
+   both shapes). *)
 let test_easter_extreme_2038_late_modern () =
   check ~msg:"2038-04-24 Holy Saturday: still Passiontide, violet (RG 128)" 2038 4 24
     "2038-04-24 saturday season=passiontide week=2 slug=ef-passiontide-2-saturday rank=class-1 colour=violet subject=lord \
      name_la=Sabbato sancto comms=[] in=- out=[]";
   check ~msg:"2038-04-25 late-modern instance of the latest possible Easter (Gauss-verified)" 2038 4 25
     "2038-04-25 sunday season=paschaltide week=1 slug=ef-easter-sunday rank=class-1 colour=white subject=temporal name_la=- comms=[] in=- \
-     out=[]"
+     out=[major-litanies->2038-04-27]";
+  check ~msg:"2038-04-27 Easter+2: the Litanies' own transfer target, commemorated and privileged" 2038 4 27
+    "2038-04-27 tuesday season=paschaltide week=1 slug=ef-easter-1-tuesday rank=class-1 colour=white subject=temporal \
+     name_la=- comms=[major-litanies:privileged] in=- out=[]"
 
 (* ------------------------------------------------------------------ *)
 (* Annunciation transfer, 25 March inside Holy Week (register §4, RG 96
@@ -958,6 +994,91 @@ let test_bvm_saturday_excludes_mt_carmel_2033 () =
      rank=class-4 colour=white subject=bvm name_la=Officium sanctae Mariae in sabbato comms=[] in=- out=[]"
     (describe d)
 
+(* ------------------------------------------------------------------ *)
+(* RG 80/81/109(f), the Major Litanies (ef-major-litanies task). Every
+   date below independently derived from the primary text, not read off a
+   `colitur day` run first and rationalised (this file's own header, rule
+   3): Easter's own date for each civil year comes from Computus (already
+   independently Gauss-cross-checked by this file's own extreme-year
+   pins), 25 April's Easter-offset and weekday follow arithmetically from
+   that, and the RULE applied at each offset (RG 80's transfer condition;
+   RG 91 entries 15/16 for the Sunday-vs-Mark band comparison; RG 111(b)'s
+   privilege-overrides-ordinary clause) is quoted at
+   Rite_ef.Precedence_ef's own [disposition]/[admit]/[transfer_target] and
+   at data/ef/expected-divergences-missalemeum.sexp's own M5/M20 entries,
+   which independently adjudicate the one substantive rubric question here
+   (WHO wins the Sunday's single slot) against the missalemeum oracle. *)
+(* ------------------------------------------------------------------ *)
+
+(* The ORDINARY case (~97.7% of years, register's own measurement): 25
+   April 2026 is a Saturday (independently checked via `date -d
+   2026-04-25 +%A`, this file's own header rule 2), Easter+20 (Easter 2026
+   = 5 April, itself independently checked the same way against a
+   published 2026 Easter date). St Mark (II class, RG 91 entry 16) wins the day outright
+   over the ordinary Class4 Paschaltide feria (entry 28); the Litanies,
+   Commemoration_only, is the day's ONLY other candidate and is admitted
+   uncontested ({!Rite_ef.Precedence_ef.admit}'s [Class2, false] case: one
+   slot, table order alone, no rival). This is the SAME date and shape
+   data/ef/expected-divergences-missalemeum.sexp's own [M5] entry
+   adjudicates against the real missalemeum oracle (verdict colitur, a
+   naming-convention difference only -- "The Major Litanies" vs
+   missalemeum's own "Pro rogationibus"). *)
+let test_major_litanies_ordinary_2026 () =
+  check ~msg:"2026-04-25: St Mark observed outright (RG91 e16 > e28); the Major Litanies (RG80/109(f)) ride \
+              along uncontested" 2026 4 25
+    "2026-04-25 saturday season=paschaltide week=3 slug=mark rank=class-2 colour=red subject=saint name_la=- \
+     comms=[major-litanies:privileged] in=- out=[]"
+
+(* The FOUR Sunday-displacement years in 2005-2050 (this task's own
+   measurement, register): 25 April is a Sunday, so St Mark (entry 16, II
+   class) loses to it exactly as any other II-class feast would (entry 15
+   < entry 16), becoming an ordinary commemoration CANDIDATE rather than
+   the observed day -- and then loses the day's own single slot to the
+   Litanies (RG 111(b): "quæ tamen omittitur si commemoratio privilegiata
+   facienda sit" -- the ordinary de-festo-II-classis commemoration is
+   DROPPED once a privileged one is due). [omitted_has] on each date below
+   confirms Mark is genuinely reported dropped, not silently absent --
+   "omitted: admission limit reached", {!Precedence.resolve}'s own generic
+   reason for a candidate [disposition] admitted to the contest but
+   [admit] then cut. Two different generic Sunday slugs appear (week 4 in
+   2010/2021, week 5 in 2027/2032) because Easter falls on a different
+   date in each pair -- neither is hand-picked, both are what
+   [Temporal_ef.sunday_slug] actually computes. *)
+let test_major_litanies_displaces_mark_on_ii_class_sunday () =
+  List.iter
+    (fun (y, week) ->
+      let d = fetch y 4 25 in
+      Alcotest.(check bool)
+        (Printf.sprintf "%d-04-25: St Mark is in [omitted] (RG111(b)'s privileged-commemoration override), not \
+                          silently dropped" y)
+        true (omitted_has d "mark");
+      Alcotest.(check string)
+        (Printf.sprintf "%d-04-25: the Sunday observed (II class); ONLY the Litanies commemorated, Mark \
+                          displaced (RG111(b))" y)
+        (Printf.sprintf
+           "%d-04-25 sunday season=paschaltide week=%d slug=ef-easter-sunday-%d rank=class-2 colour=white \
+            subject=temporal name_la=- comms=[major-litanies:privileged] in=- out=[]"
+           y week week)
+        (describe d))
+    [ (2010, 4); (2021, 4); (2027, 5); (2032, 5) ]
+
+(* The OTHER RG 80 trigger shape, complementing 1666/2038 above (Easter
+   Sunday itself = 25 April): here Easter MONDAY = 25 April (Easter = 24
+   April 2011, independently Gauss-derivable and already the domain's own
+   register-cited "Easter Monday" marker, [ef-easter-1-monday]). RG 80's
+   "following Tuesday" is one day later this time (26 April, not 27) --
+   both shapes converge on the SAME offset, Easter+2, never on a fixed
+   civil-date difference. *)
+let test_major_litanies_transfer_2011_easter_monday () =
+  check ~msg:"2011-04-25 Easter Monday (RG80's SECOND trigger): Litanies depart for the following Tuesday, \
+              26 April" 2011 4 25
+    "2011-04-25 monday season=paschaltide week=1 slug=ef-easter-1-monday rank=class-1 colour=white \
+     subject=temporal name_la=- comms=[] in=- out=[major-litanies->2011-04-26]";
+  check ~msg:"2011-04-26 Easter+2: the Litanies land here, commemorated and privileged, exactly one day after \
+              origin (not two, unlike the Easter-Sunday shape)" 2011 4 26
+    "2011-04-26 tuesday season=paschaltide week=1 slug=ef-easter-1-tuesday rank=class-1 colour=white \
+     subject=temporal name_la=- comms=[major-litanies:privileged] in=- out=[]"
+
 let suite =
   ( "golden pins (known-tricky years)",
     [ Alcotest.test_case "Easter extreme: 1598 earliest (22 Mar, Gauss-verified)" `Quick
@@ -1026,5 +1147,14 @@ let suite =
       Alcotest.test_case
         "RG112(d), fix round 1 (F1): the BVM Saturday office excludes Mt Carmel's own commemoration \
          (2033-07-16)"
-        `Quick test_bvm_saturday_excludes_mt_carmel_2033
+        `Quick test_bvm_saturday_excludes_mt_carmel_2033;
+      Alcotest.test_case "RG80/109(f): the Major Litanies, ordinary year, St Mark wins outright (2026-04-25)"
+        `Quick test_major_litanies_ordinary_2026;
+      Alcotest.test_case
+        "RG111(b): the Major Litanies displace St Mark's own commemoration on a II-class Sunday (2010, 2021, \
+         2027, 2032)"
+        `Quick test_major_litanies_displaces_mark_on_ii_class_sunday;
+      Alcotest.test_case
+        "RG80's second trigger: Easter Monday = 25 April, the Litanies transfer to Easter+2 (2011)" `Quick
+        test_major_litanies_transfer_2011_easter_monday
     ] )