Merge branch 'ef-bvm-saturday': the Office of Our Lady on Saturday

Builds RG 91 entry 27 under RG 78 -- 'In sabbatis, in quibus occurrit
Officium de feria IV classis, fit de sancta Maria in sabbato' -- a rank
test, not a season list. band had been assigning entry 27 312966 times
across the domain while the office was never constructed, so an
otherwise-unoccupied Saturday got a bare ferial slug and its season's
colour.

75863 days change, in two shapes: colour (green or violet to white) on
74642, and colour plus a dropped commemoration on 1221. The 312966
reconciles to the day across four buckets, 210808 of them impeded by a
sanctoral winner.

The first version introduced a live RG 112(d) violation on every
Saturday falling on 16 July: the Office of Our Lady observed,
commemorating Our Lady. Both photographic scans print a rubric at that
Mass for exactly this collision -- 'Missa dici potest aut de sancta
Maria in sabbato, aut propria' -- absent from the electronic
transcription, and cited nowhere. It was missed because the check was a
grep for subject = Bvm, and Mt Carmel is tagged Saint: the rubric's
criterion is whose intercession the oration implores, not colitur's own
tag.

The I-V Mass numbering is a propers rotation and stays unbuilt;
citations remain empty on all 3073916 days.

Recorded rather than glossed: the new rule has no comparison-layer
witness at all, and lectio's fixture prints a Mt Carmel commemoration on
8 in-window dates where colitur now prints none -- a real divergence
that falls through a gap in what the comparators examine. Time after
Epiphany's 5015 office days have zero oracle witnesses and rest on the
scan alone.

1 files changed, 51 insertions, 2 deletions

diff --git a/test/test_differential.ml b/test/test_differential.ml
index bea1bf4..5093484 100644
--- a/test/test_differential.ml
+++ b/test/test_differential.ml
@@ -138,6 +138,7 @@ module Slug = Colitur_kernel.Slug
 module Date = Colitur_kernel.Date
 module Cel = Colitur_kernel.Celebration
 module Colour = Colitur_kernel.Colour
+module Subject = Colitur_kernel.Subject
 module V = Rite_ef.Vocab_ef
 
 (* Same relative paths test_rite_ef.ml/test_sanctoral_ef.ml use: dune test
@@ -216,6 +217,14 @@ type row = {
   slug : string;
   rank : string;
   colour : string;
+  (* Fix round 1 (coordinator finding F3): ONLY ever populated for colitur's
+     own row (see [colitur_rows_2005_2050] below) -- lectio's own fixture
+     format has no subject column at all, so [row_of_line] (the lectio-side
+     parser) sets this to "-", a placeholder never read on that side. Every
+     Layer C predicate that reads [subject] must therefore read it off the
+     COLITUR row [c], never [l] -- the same asymmetry [row]'s other fields
+     do not have, called out here rather than left implicit. *)
+  subject : string;
 }
 
 let read_lines path =
@@ -232,7 +241,7 @@ let read_lines path =
 let row_of_line line =
   match String.split_on_char ' ' line with
   | date :: weekday :: season :: week :: slug :: rank :: colour :: _others ->
-      { date; weekday; season; week; slug; rank; colour }
+      { date; weekday; season; week; slug; rank; colour; subject = "-" }
   | _ -> Alcotest.failf "malformed fixture line (fewer than 7 fields): %S" line
 
 let lectio_rows () = List.map row_of_line (read_lines fixture_path)
@@ -271,7 +280,8 @@ let colitur_rows_2005_2050 () =
               week;
               slug = Slug.to_string cel.Cel.slug;
               rank = V.rank_to_string cel.Cel.rank;
-              colour = Colour.to_string cel.Cel.colour
+              colour = Colour.to_string cel.Cel.colour;
+              subject = Subject.to_string cel.Cel.subject
             }
             :: !rows
       | None -> Alcotest.failf "internal error: no resolved day for %s" (Date.to_iso8601 !d));
@@ -516,6 +526,44 @@ let holy_name_fallback_dates_2005_2050 =
     "2034-01-02"; "2035-01-02"; "2036-01-02"; "2040-01-02"; "2041-01-02"; "2045-01-02";
     "2046-01-02"; "2047-01-02" ]
 
+(* C17 -- ef-bvm-saturday task: RG 91 entry 27 ("Officium sanctae Mariae in
+   sabbato" -- see data/ef/expected-divergences.sexp's own C17 note for the
+   full RG 78/RG 120(b) citation). lectio builds no equivalent office at all
+   (checked directly against its own tridentine-calendar.ini/generator, the
+   same "genuine upstream gap, not a colitur bootstrap miss" shape C15/C16
+   already document for their own gaps) -- it shows the ordinary season
+   colour on every otherwise-unoccupied Class4 Saturday where colitur's own
+   RG 78 fix now shows white. Season, slug and rank all still agree --
+   temporal_ef.ml's own [bvm_saturday_names] citation ("Slug" paragraph)
+   deliberately REUSES the ordinary ferial slug rather than minting a new
+   one, precisely so this predicate's diff set stays [Colour_f] alone, never
+   [Slug_f] too. Gated on colitur's own [rank]/[weekday]/[colour] rather
+   than a date list, the same shape M2 (data/ef/expected-divergences-
+   missalemeum.sexp) already uses for the identical reason: this
+   population is large (a large fraction of all Saturdays domain-wide) and
+   entirely formulaic (RG 78's own condition, "otherwise unoccupied
+   IV-class Saturday", reduces exactly to this triple), not a short,
+   individually-interesting list of dates the way C14/C15/C16 above are. *)
+let is_bvm_saturday_row (c : row) diffs =
+  (* Fix round 1 (coordinator finding F3): [c.subject] added -- the ONLY
+     field in this predicate that pins WHICH celebration is observed, not
+     merely its shape. Every other Layer C entry pins a colitur slug (C1's
+     own [jan_6_13_slug], C6's [nativity_octave_day_slugs], C8/C14/C15/C16's
+     own literal slug checks); this entry could not, because the office
+     deliberately REUSES the ordinary ferial slug (Rite_ef.Temporal_ef's own
+     [bvm_saturday_names] citation, "Slug" paragraph) -- there is no fixed
+     slug string to pin. [subject = "bvm"] is the field that DOES uniquely
+     identify the office (set nowhere else the differential's own
+     [colitur_rows_2005_2050] can produce a Saturday/Class4/white
+     combination for), closing the gap a shape-only predicate left open:
+     without this conjunct, a FUTURE bug that made some OTHER white,
+     Class4, Saturday candidate exist (Christmastide/Paschaltide, where
+     [season_colour] is already white, so a real bug there could slip
+     through unnoticed by colour alone) would be silently absorbed here
+     too. *)
+  diffs = [ Colour_f ] && String.equal c.weekday "saturday" && String.equal c.rank "class-4"
+  && String.equal c.colour "white" && String.equal c.subject "bvm"
+
 (* [layer_c_reason l c diffs] returns the [data/ef/expected-divergences.sexp]
    [id] this row-pair's remaining (post Layer A/B) diff set belongs to, or
    [None] if nothing here explains it (a genuine, uncovered failure). *)
@@ -571,6 +619,7 @@ let layer_c_reason (l : row) (c : row) diffs =
     && subset diffs [ Slug_f; Rank ]
     && String.equal c.slug "ef-holy-name"
   then Some "C16"
+  else if is_bvm_saturday_row c diffs then Some "C17"
   else None
 
 (* ---------------------------------------------------------------------- *)