data(ef): close and derive the RG 91 entry 27 allow-list rows

The BVM Saturday office is now genuinely correct, so both comparators'
allow-lists move -- every count derived from the harnesses' own failure
output, never transcribed or guessed.

lectio differential (data/ef/expected-divergences.sexp, C17, new,
colitur): lectio builds no equivalent office at all, so it keeps
showing the plain season colour on every otherwise-unoccupied Class4
Saturday where colitur now shows white. Season, slug and rank all still
agree (the office deliberately reuses the ordinary ferial slug), so
Colour_f alone is the complete diff set -- gated on colitur's own
rank/weekday/colour rather than a date list, the same shape M2 used, at
416 rows over 2005-2050.

missalemeum oracle (data/ef/expected-divergences-missalemeum.sexp): M2
is CLOSED, REMOVED, the same shape as this file's own M4/M6/M7/M9/M12/
M14/M17 precedents -- not re-adjudicated to a different verdict, gone
because the colour divergence it named no longer occurs on any of its
former 22 dates. What is left on all 22 is Observed_identity_unresolved
alone (colitur's BVM-Saturday candidate is temporal-origin and
deliberately carries no English name) -- exactly M18's own shape, not a
distinct citation any more. Keeping M2 as a separate id would have kept
silently absorbing these rows under a stale "colour differs" citation
whose own reason had stopped firing (subset's own diff-set test admits
a SMALLER set than the one named) -- the same "count proving cardinality
where identity was required" trap this project's review process
watches for. M18's own expected_rows moves 373 -> 395 accordingly.

2 files changed, 59 insertions, 31 deletions

diff --git a/test/test_differential.ml b/test/test_differential.ml
index bea1bf4..3f416fd 100644
--- a/test/test_differential.ml
+++ b/test/test_differential.ml
@@ -516,6 +516,28 @@ 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 =
+  diffs = [ Colour_f ] && String.equal c.weekday "saturday" && String.equal c.rank "class-4"
+  && String.equal c.colour "white"
+
 (* [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 +593,7 @@ 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
 
 (* ---------------------------------------------------------------------- *)
diff --git a/test/test_oracle.ml b/test/test_oracle.ml
index 58ceb26..c0badfe 100644
--- a/test/test_oracle.ml
+++ b/test/test_oracle.ml
@@ -475,25 +475,30 @@ let contains_substring s ~needle =
    own "in dominica quavis" (ANY Sunday, unqualified) -- verdict colitur. *)
 let m1_dates = [ "2026-06-28"; "2026-08-09" ]
 
-(* M2 -- RG 91 entry 27 ("Officium sanctae Mariae in sabbato"): every
-   otherwise-unoccupied IV-class Saturday should carry the votive Office of
-   the BVM (white; missalemeum's own title cycles "I".."V Mass of the
-   B. V. M. - Salve, Sancta Parens"), a genuinely DISTINCT office from an
-   ordinary green/violet feria. temporal_ef.ml's [band] already carries an
-   entry-27 comment acknowledging this row of RG 91 exists, but nothing in
-   [Temporal_ef.temporal]'s actual CONSTRUCTION builds this office -- an
-   unimpeded Time-after-Epiphany/-Pentecost Saturday still gets the bare
-   ferial slug and [season_colour]'s green. A genuine, primary-attested
-   FEATURE GAP (not a citation dispute) -- verdict missalemeum: colitur is
-   short a whole office here, not merely differently-opinioned. Registered
-   as an open item (register §6) rather than built in this task: it needs
-   its own proper texts/citations, the same scope line "Major Litanies"
-   (M5 below) already sits on. Matched on the oracle's own title substring,
-   not a hardcoded date list -- the title IS the distinguishing evidence,
-   and every Paschaltide occurrence (where colitur's season colour is
-   already white, RG 119) never reaches this predicate at all, since its
-   diffs are already empty before [layer_m_reason] is ever called. *)
-let bvm_saturday_title = "Salve, Sancta Parens"
+(* M2 -- CLOSED, REMOVED (ef-bvm-saturday task), same shape as M12/M17's own
+   removal elsewhere in this suite (not re-adjudicated to a different
+   verdict, gone because the underlying divergence stopped occurring): RG 91
+   entry 27 ("Officium sanctae Mariae in sabbato") is now built
+   (Rite_ef.Temporal_ef's own [bvm_saturday_names] citation has the full RG
+   78/RG 120(b) argument) -- white, unconditionally, on every otherwise-
+   unoccupied IV-class Saturday, so [Colour_f] no longer appears in this
+   predicate's own diff set on ANY of these 22 dates (checked: 0 of them
+   retain it). What is left on every one of them is [Observed_identity_
+   unresolved] ALONE -- colitur's own BVM-Saturday candidate is
+   temporal-origin and deliberately carries no ENGLISH name (Latin only,
+   the same zero-circularity discipline Holy Family/Holy Name/the Sacred
+   Triduum already established) -- which is EXACTLY [M18]'s own shape
+   ([diffs = [ Observed_identity_unresolved ]], nothing else disagreeing),
+   not a distinct citation any more. Kept as a separate id here would have
+   been the same "count proving cardinality where identity was required"
+   trap this project's own review process watches for: [subset] admits a
+   SMALLER diff set than the one named, so this branch would have kept
+   silently absorbing these 22 rows under a stale "colour differs" citation
+   even though that citation's own reason no longer fires -- checked
+   directly, not assumed: removing this branch and re-running moves the
+   count from M2's own former 22 to M18's own count rising by exactly 22
+   (373 -> 395, see M18's own note below), with the "no unexplained
+   differences" test staying green throughout. *)
 
 (* M3 -- RG 87 (Minor Litanies/Rogations): the SAME gap the lectio
    differential's own C8 already names (data/ef/expected-divergences.sexp)
@@ -822,7 +827,12 @@ let m19_commemoration_matches (c : colitur_row) =
   | [ (slug, _, _, _) ] -> String.equal slug "commemoration-of-st-peter"
   | _ -> false
 
-let layer_m_reason (c : colitur_row) (o : oracle_row) diffs =
+(* [_o] (the oracle's own row) is unused now that M2 -- its one reader, via
+   [o.o_title] -- is closed/removed (see the comment above [m1_dates]):
+   every remaining predicate below reads only [c]/[diffs]. Kept as a named,
+   typed parameter (not dropped from the signature) so a FUTURE oracle-title
+   predicate has somewhere to plug back in without a signature change. *)
+let layer_m_reason (c : colitur_row) (_o : oracle_row) diffs =
   if diffs = [] then None
   (* M1's own subset widened (this task): colitur's observed day on both
      dates is TEMPORAL-origin (the Sunday itself, RG33's own point -- the
@@ -832,17 +842,12 @@ let layer_m_reason (c : colitur_row) (o : oracle_row) diffs =
   else if List.mem c.c_date m1_dates
           && subset diffs [ Rank; Colour_f; Comm_presence; Observed_identity_unresolved ]
   then Some "M1"
-  (* M2's own subset widened (this task): every BVM-Saturday date's observed
-     celebration is temporal-origin (the ordinary Saturday feria colitur
-     computes, not the distinct Office of the BVM missalemeum's title
-     names -- M2's own gap), so [Observed_identity_unresolved] now fires
-     alongside [Colour_f] where it used to fire alone, AND alone on its own
-     on every Paschaltide occurrence M2's own comment already says never
-     reached this predicate before (colour already agrees there; only the
-     new axis has anything left to say). *)
-  else if contains_substring o.o_title ~needle:bvm_saturday_title
-          && subset diffs [ Colour_f; Observed_identity_unresolved ]
-  then Some "M2"
+  (* M2 -- CLOSED, REMOVED (ef-bvm-saturday task): see this file's own M2
+     note above (near [m1_dates]) for the full account -- the RG 91 entry 27
+     office is now built, so every one of these 22 dates now falls through
+     to [M18]'s own generic predicate below instead ([diffs = [
+     Observed_identity_unresolved ]] exactly), which is what actually
+     catches them now. *)
   (* M3's own subset widened (this task): the Rogation Monday feria colitur
      observes is temporal-origin, same root cause as M1/M2 above. *)
   else if List.mem c.c_date m3_dates && subset diffs [ Colour_f; Observed_identity_unresolved ] then