kernel(precedence-ef): fix precedence_ef.mli's stale RG33/RG26/RG111(b) contract

The .mli's disposition doc still said a Class1-or-Class2 vigil is Omit
(RG 33) -- the pre-Task-16 mistranscription the register corrects at its
RG 33 entry. The .ml has read Class2 || Class3 since commit 079e332; the
.mli never caught up. It also named only vigil_suffix, when the vigil
test the code actually runs also checks vigil_prefix (the shape the
sanctoral bootstrap's four real vigils use); omitted RG 26's Class4
temporal-ferias-are-never-commemorated branch entirely, then asserted the
listed cases 'exhaust every representable shape', which was false as
written; and omitted RG 111(b)'s 'de festo II classis' rank floor from
admit's doc, describing only the privilege-override half of that rule.

Fixed all four: the vigil-omission bullet now names Class2/Class3 and
both slug conventions; the missing RG 26 branch is now documented,
folding the exhaustiveness claim into an accurate five-branch count;
admit's Sunday case now states the rank floor as a second, independent
condition.

The same stale RG 109(e) reading this interface carried ('leaves the
Advent and Lent Ember sets ordinary') also survived as the stated reason
september_ember_prefix exists, in the .ml, about 330 lines from the
already-corrected privilege_of comment it contradicts. Fixed there too:
September is broken out because it sits outside RG 109(e)'s three named
seasons entirely, not because Advent/Lent Ember needs excluding from (e)
-- it does not, per privilege_of's own corrected comment.

No behaviour change: both fixes are doc-comment-only edits to already-
correct code (precedence_ef.ml's disposition/admit implementations were
fixed in an earlier commit; only the .mli's prose and one earlier .ml
comment lagged).

2 files changed, 84 insertions, 42 deletions

diff --git a/lib/rites/rite_ef/precedence_ef.ml b/lib/rites/rite_ef/precedence_ef.ml
index 88f1a54..bfd3b93 100644
--- a/lib/rites/rite_ef/precedence_ef.ml
+++ b/lib/rites/rite_ef/precedence_ef.ml
@@ -87,10 +87,18 @@ let is_vigil slug =
 
    [september_ember_prefix] is broken out as its own name (rather than an
    anonymous list literal) because Task 9's [privilege_of] needs to test the
-   September set alone, RG 109 privileging it while leaving the Advent and
-   Lent sets ordinary (register lines 375-376) -- building [ember_prefixes]
-   from it rather than duplicating the literal keeps the two from silently
-   drifting apart. *)
+   September set alone: RG 109(e)'s three named seasons (Advent, Lent,
+   Passiontide, §4 "Commemorations") never include September, which sits
+   entirely in time after Pentecost under any reading -- so September Ember
+   days need their own separate privilege category, (d), regardless of how
+   (e) itself is read. CORRECTED (fix round 1, F1/F2): this comment
+   previously justified the split the other way round, claiming RG 109(e)
+   privileges September specifically "while leaving the Advent and Lent
+   sets ordinary" -- WRONG; see [privilege_of]'s own (e) comment below for
+   the full argument. The Advent and Lent Ember sets ARE privileged under
+   (e), the same as any other Advent/Lent feria; building [ember_prefixes]
+   from this constant rather than duplicating the literal keeps the two
+   from silently drifting apart. *)
 let advent_ember_prefix = "ef-advent-ember-"
 let lent_ember_prefix = "ef-lent-ember-"
 let september_ember_prefix = "ef-september-ember-"
diff --git a/lib/rites/rite_ef/precedence_ef.mli b/lib/rites/rite_ef/precedence_ef.mli
index 8234bf3..161d890 100644
--- a/lib/rites/rite_ef/precedence_ef.mli
+++ b/lib/rites/rite_ef/precedence_ef.mli
@@ -65,8 +65,8 @@ val unclassified : int
 (** [band ctx c]: RG 91's Table of Precedence. Returns the table's own entry
     number -- I class 1-13, II class 14-21, III class 22-26, IV class 27-28;
     lower wins (see {!Precedence.rules.band}) -- EXCEPT where the table's own
-    text states an exception: entry 8 (All Souls, register line 334) reads
-    "yields to an occurring Sunday", so on a Sunday this returns a value that
+    text states an exception: entry 8 (All Souls) reads "yields to an
+    occurring Sunday", so on a Sunday this returns a value that
     loses to entry 15 rather than the literal integer 8 (see the comment on
     entry 8 in precedence_ef.ml for the exact value and why). Total over
     every candidate {!Precedence.resolve} or {!Calendar} can construct,
@@ -82,39 +82,62 @@ val band : Vocab_ef.season Precedence.context -> Vocab_ef.rank Precedence.candid
     somewhere to be caught other than a silently-wrong RG 33 disposition. *)
 val sunday_marker : string
 
-(** [disposition ~winner ~loser]: RG 92-95, 33, 94 (docs/research/
-    rules-register.md §4, "Occurrence" and "Vigils"). What becomes of a
-    losing candidate, decided by the LOSER's own rank and status (RG 95),
-    except RG 33's vigil omission, which also reads the winner:
+(** [disposition ~winner ~loser]: RG 92-95, 33, 21-27, 94 (docs/research/
+    rules-register.md §4, "Occurrence", "Vigils" and "Caput IV, 'De
+    feriis'"). What becomes of a losing candidate, decided by the LOSER's
+    own rank and status (RG 95), except RG 33's vigil omission, which also
+    reads the winner:
     - a {!Celebration.status} of [Commemoration_only] is always
       [Commemorate] (checked first: it can never win -- see
       {!Precedence.resolve} -- and, by that same status's own definition,
       already denotes an office with nothing left to translate, so it never
       transfers either; not itself a further RG citation beyond RG 93's
       general four-mechanism statement above);
-    - a [Class1] or [Class2] loser whose slug marks it a vigil ({!vigil_suffix})
-      is [Omit] when the winner is any Sunday ({!sunday_marker}) or itself
-      [Class1] (RG 33 -- entirely omitted, not merely commemorated);
+    - a [Class2] or [Class3] loser whose slug marks it a vigil
+      ({!vigil_suffix} OR {!vigil_prefix} -- both conventions this
+      codebase's data uses, see {!vigil_prefix}'s own comment) is [Omit]
+      when the winner is any Sunday ({!sunday_marker}) or itself [Class1]
+      (RG 33 -- entirely omitted, not merely commemorated). A [Class1]
+      vigil (Nativity, Pentecost) is outside RG 33 entirely -- RG 30 makes
+      it preferred to any feast whatsoever, so a real one can never reach
+      this function as a [loser] in the first place (see the .ml's own
+      comment on [is_omissible_vigil] for the full argument);
     - any other [Class1] loser that is NOT a Sunday ({!sunday_marker}) is
-      [Transfer] (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, from feasts, entries 11-13, so a Sunday is
-      never a "feast" in RG 95's sense and does not transfer even when
-      impeded by a higher I-class day. This is also what moves All Souls,
-      register line 334, once it loses to an occurring Sunday -- WHERE it
-      lands is {!Rite.t.transfer_target}'s job, not this function's);
-    - everything else -- including an impeded I-class Sunday -- is
-      [Commemorate], carrying its real RG 109 privilege (see {!admit}
-      below); RG 109(a) (register line 374) lists "of a Sunday" as a
-      privileged commemoration category precisely because an impeded Sunday
-      stays put rather than moving to another day.
+      [Transfer] (RG 95 -- only I-class FEASTS have the right of
+      translation; RG 91's own table lists Sundays as a separate row, entry
+      6, from feasts, entries 11-13, so a Sunday is never a "feast" in RG
+      95's sense and does not transfer even when impeded by a higher
+      I-class day. This is also what moves All Souls, RG 91 entry 8, once
+      it loses to an occurring Sunday -- WHERE it lands is
+      {!Rite.t.transfer_target}'s job, not this function's);
+    - a TEMPORAL-origin, non-vigil loser of [Class4] is [Omit] (RG 26,
+      "Caput IV, De feriis" -- "every feria not named in [RG 23-25] is IV
+      class ... and IV-class ferias are NEVER commemorated." A SEPARATE
+      rule from RG 109's honour-class one immediately below, keyed on
+      ferial CLASS rather than on RG 109's privilege letters: RG 109 sorts
+      commemorations that already exist into honour classes (RG 108's
+      differing liturgical hours), it does not itself decide which offices
+      have the right to be commemorated at all -- that is Caput IV's own
+      business. A SANCTORAL loser of the same rank is unaffected by this
+      branch (the [is_temporal] guard): RG 21 defines "feria" as any
+      weekday, never a saint's day, and RG 111(c)/(d) admit an "ordinary"
+      commemoration of a losing SAINT freely, with no such class-keyed
+      gate);
+    - everything else -- including an impeded I-class Sunday, and a
+      SANCTORAL loser of any rank below I class -- is [Commemorate],
+      carrying its real RG 109 privilege (see {!admit} below); RG 109(a)
+      lists "of a Sunday" as a privileged commemoration category precisely
+      because an impeded Sunday stays put rather than moving to another
+      day, and RG 24/25 make a losing II- or III-class FERIA's own
+      commemoration mandatory when impeded, not merely eligible.
 
     Total over every winner/loser pair {!Precedence.resolve} or {!Calendar}
     can construct: [Vocab_ef.rank] (RG 8) and {!Celebration.status} are both
-    closed variants, so the cases above exhaust every representable shape --
-    there is no fifth, "unclassified" case the way {!band} needs one,
-    because this function's own return type has no such slot to fall into
-    by accident. *)
+    closed variants, and the five cases above -- an if/else-if chain ending
+    in the unconditional [Commemorate] catch-all -- exhaust every value
+    those two fields can take between them; there is no fifth,
+    "unclassified" case the way {!band} needs one, because this function's
+    own return type has no such slot to fall into by accident. *)
 val disposition :
   winner:Vocab_ef.rank Precedence.candidate ->
   loser:Vocab_ef.rank Precedence.candidate ->
@@ -130,26 +153,37 @@ val disposition :
 val nativity_octave_prefix : string
 
 (** The September set of {!ember_prefixes}, broken out on its own because RG
-    109(d) privileges September Ember days specifically while leaving the
-    Advent and Lent sets (also {!ember_prefixes}) ordinary -- register lines
-    375-376. {!ember_prefixes} is built from this constant, not a duplicated
-    literal, so the two cannot silently drift apart. *)
+    109(d) (§4, "Commemorations") privileges September Ember days under its
+    own name, and September sits outside RG 109(e)'s three named seasons
+    (Advent, Lent, Passiontide) under any reading of that clause -- NOT
+    because the Advent and Lent Ember sets need excluding from (e), which
+    they do not: (e)'s own bare text privileges them too, the same as any
+    other Advent/Lent feria (see {!Precedence_ef.privilege_of}'s own (e)
+    comment in the .ml for the full argument, corrected fix round 1).
+    {!ember_prefixes} is built from this constant, not a duplicated literal,
+    so the two cannot silently drift apart. *)
 val september_ember_prefix : string
 
 (** [admit ~observed comms]: RG 108-111 (docs/research/rules-register.md §4,
-    "Commemorations", register lines 371-379). How many of [comms] -- each
-    already tagged with its real RG 109 privilege by {!disposition} -- RG
-    111 admits, and which, given the day actually observed:
+    "Commemorations"). How many of [comms] -- each already tagged with its
+    real RG 109 privilege by {!disposition} -- RG 111 admits, and which,
+    given the day actually observed:
     - [observed] a [Class1] day: none, except at most one privileged
       commemoration (the highest-dignity one, if several are due) -- an
       ordinary one is never admitted here, no matter how many are due;
-    - [observed] a [Class2] Sunday (its slug carries {!sunday_marker}): one
-      -- a privileged commemoration takes the day's one slot over any
-      ordinary one whenever one is due, not by comparing dignity, so an
-      ordinary commemoration that would otherwise win on dignity is still
-      dropped;
+    - [observed] a [Class2] Sunday (its slug carries {!sunday_marker}): one,
+      subject to TWO conditions, not one -- (i) a privileged commemoration,
+      whenever due, categorically takes the day's one slot over any
+      ordinary one, not by comparing dignity, so an ordinary commemoration
+      that would otherwise win on dignity is still dropped; (ii) failing
+      that, the slot is reserved for a [Class2] candidate SPECIFICALLY
+      ("de festo II classis", RG 111(b)'s own wording -- a RANK FLOOR, not
+      "whichever ordinary candidate has the best dignity"): a III- or
+      IV-class ordinary loser has no standing for this slot at all and is
+      admitted nothing, even when it is the only candidate due;
     - [observed] any other [Class2] day: one, by dignity alone -- no
-      privilege override, unlike the Sunday case immediately above;
+      privilege override and no rank floor, unlike the Sunday case
+      immediately above;
     - [observed] a [Class3] or [Class4] day: at most two, by dignity alone.
 
     "Dignity" here is [Vocab_ef.rank] (RG 8's four classes), NOT {!band}'s