rite(ef): an impeded I-class Sunday commemorates, not transfers

disposition's Class1 branch was unconditional on rank, so an impeded
I-class Sunday (Advent/Lent/Passiontide/Low Sunday) currently
transferred like a feast. RG 95 (register lines 323, 363) restricts the
right of translation to I-class FEASTS -- RG 91's own table lists
Sundays as a separate row (entry 6, line 332) from feasts (entries
11-13, lines 337-339) -- and RG 109(a) (line 374) lists "of a Sunday"
as a privileged commemoration category, which presupposes an impeded
Sunday stays put rather than moving to another day.

Excludes is_sunday_slug losers from the Transfer branch so they fall
through to the existing Commemorate (privilege_of loser) branch, which
already tags them Privileged via RG 109(a) with no further change.

Fires on real dates in the 2005-2050 differential window: 24 December
on Advent IV in 2023, 2028, 2034, 2045; 8 December on an Advent Sunday
in 2024, 2030, 2041.

Verified no previously-passing Transfer assertion used a Sunday-shaped
loser (grepped test_precedence_ef.ml, test_calendar.ml -- which uses
its own synthetic rite unrelated to Precedence_ef.disposition --
test_colitur.ml, test_validate.ml); confirmed by mutation-reverting the
fix and observing exactly the one new test fail, nothing else.

1 files changed, 25 insertions, 11 deletions

diff --git a/lib/rites/rite_ef/precedence_ef.ml b/lib/rites/rite_ef/precedence_ef.ml
index 06bbf7c..ff6f991 100644
--- a/lib/rites/rite_ef/precedence_ef.ml
+++ b/lib/rites/rite_ef/precedence_ef.ml
@@ -383,20 +383,34 @@ let disposition ~(winner : Vocab_ef.rank Precedence.candidate)
        I-class vigil (Nativity, Pentecost) impeded on its own Sunday/
        I-class-feast terms would wrongly transfer instead of vanishing. *)
     Precedence.Omit
-  else if cel.Celebration.rank = Class1 then
-    (* RG 95: only I-class feasts have the right of translation. This is the
+  else if
+    cel.Celebration.rank = Class1
+    && not (is_sunday_slug (Slug.to_string cel.Celebration.slug))
+  then
+    (* RG 95 (register lines 323, 363): only I-class FEASTS have the right
+       of translation -- RG 91's own table lists Sundays as a separate row
+       (entry 6, register line 332) from feasts (entries 11-13, register
+       lines 337-339), so a Sunday is never a "feast" in RG 95's sense, and
+       [is_sunday_slug] (the same marker RG 33's [impedes_vigil] and RG
+       109(a)'s [privilege_of] already use) excludes it here. This is the
        branch that completes Task 7's All Souls fix (register line 334, RG
-       91 entry 8): All Souls is I class and not a vigil, so once it loses
-       to an occurring Sunday it reaches here and transfers -- to 3
-       November per the register, but WHERE it lands is
-       Rite.transfer_target's job (RG 96), not this function's; disposition
-       only says THAT it moves. *)
+       91 entry 8): All Souls is I class, not a vigil, and not a Sunday
+       slug, so once it loses to an occurring Sunday it still reaches here
+       and transfers -- to 3 November per the register, but WHERE it lands
+       is Rite.transfer_target's job (RG 96), not this function's;
+       disposition only says THAT it moves. *)
     Precedence.Transfer
   else
-    (* RG 95's other branch, for everything below I class: "aut
-       commemorantur aut penitus omittuntur" -- commemorated or wholly
-       omitted. Which of the two survives is RG 108-111's admission count
-       ([admit], below), not this function's decision; this only opens the
+    (* RG 95's other branch: "aut commemorantur aut penitus omittuntur" --
+       commemorated or wholly omitted. Reached by everything below I class,
+       AND by an impeded I-class Sunday (excluded from the [Transfer] branch
+       above): RG 109(a) (register line 374) lists "of a Sunday" as a
+       privileged commemoration category, which presupposes an impeded
+       Sunday stays put rather than moving to another day the way a feast
+       does -- [privilege_of] tags it [Privileged] via the same
+       [is_sunday_slug] marker, with no further code needed here. Which of
+       commemorate/omit survives is RG 108-111's admission count ([admit],
+       below), not this function's decision; this only opens the
        commemoration, tagged with its real RG 109 privilege via
        [privilege_of].