data(ef): retag the Purification and Most Holy Name of Mary as BVM, not Lord

Both entries carried (subject Lord) in data/ef/sanctoral.sexp, inherited
unchecked from lectio's own class = lord field. The calendarium says
otherwise: 2 February reads "IN PURIFICATIONE B. MARIAE VIRG." and
12 September reads "Sanctissimi Nominis Mariae" -- both name Mary, not
the Lord, unlike the four genuine Lord entries' own "D. N. I. C."
formula (Precious Blood, Transfiguration, Exaltation of the Holy Cross,
Dedication of the Archbasilica of the Most Holy Saviour), all of which
were checked against the same calendarium and left untouched.

This matters together with RG16(a): applying the rule while the
Purification was still mistagged Lord would have made it outrank an
occurring II-class Sunday and then wrongly suppress that Sunday's own
commemoration under RG16(a) too, the opposite of the intended fix.
Retagged, the Purification no longer bands at RG91 entry 14, so the
Sunday is observed and the Purification survives as its own ordinary
commemoration.

Corrected via a new data/ef/adjustments.sexp overlay (Set_subject Bvm),
the same mechanism that file already uses to suppress vigil-of-christmas
as a bootstrap duplicate, not a hand-edit of sanctoral.sexp itself: that
file's own header asks for edits to go through the generator, and its
SHA-256 provenance covers a byte-faithful mirror of lectio's INI. The
Purification retag changes which day the lectio differential observes on
2 February whenever it falls on a Sunday (six years, 2005-2050); allow-
listed as C12 in data/ef/expected-divergences.sexp, expected_rows derived
independently (date -d <year>-02-02 for each year in range), not
transcribed from a comparator run.

1 files changed, 13 insertions, 0 deletions

diff --git a/test/test_differential.ml b/test/test_differential.ml
index a9bdb91..aa75737 100644
--- a/test/test_differential.ml
+++ b/test/test_differential.ml
@@ -450,6 +450,19 @@ let layer_c_reason (l : row) (c : row) diffs =
     && subset diffs [ Slug_f; Rank; Colour_f ]
   then Some "C10"
   else if String.equal c.slug "ef-passiontide-2-thursday" && diffs = [ Colour_f ] then Some "C11"
+  (* RG16(a) task (register §6.0 + the sanctoral subject audit, this task's
+     own report): 2 February on a Sunday. colitur now observes the Sunday
+     (data/ef/adjustments.sexp retags the Purification `Bvm`, so it no
+     longer bands at RG 91 entry 14 -- only a Feast of the LORD does); the
+     Purification survives as its own commemoration, matching the register's
+     ruling, just not as [c]'s OBSERVED slug here. lectio still tags it
+     `class = lord` (unretagged upstream) and so still observes it outright.
+     Matched on [l.slug] (lectio's side), the only side that can show this
+     literal now -- colitur's own [c.slug] is whichever Sunday family the
+     date falls in (time-after-epiphany or Septuagesima), not one fixed
+     literal, unlike [c7]/[c11]'s single-slug tests above. *)
+  else if String.equal l.slug "purification-of-the-blessed-virgin-mary" && subset diffs [ Slug_f; Colour_f ]
+  then Some "C12"
   else None
 
 (* ---------------------------------------------------------------------- *)