fix(ef): Good Friday is black (RG 128(b) + RG 132)

This file's own comment called RG 132's black "a separate, unmodelled gap".
It is modelled now. RG 128(b)'s exception list carries Good Friday in the same
sentence as Holy Thursday's -- "Actione liturgica feria VI in Passione et
Morte Domini usque ad Communionem exclusive" excepts the day from
Passiontide's violet -- and RG 132 assigns black to it. Adopted from colitur,
which closed the same gap against the Missal in its v0.4.0.

The rubric is per-action and this model carries one colour per day, so black
is the day's principal colour, the same acknowledged limit the Palm Sunday
blessing already has. missalemeum's own colour set for the day is "bv", black
first, so the oracle test accepts this without a new allow-list entry.

Found by cross-checking clectio's output against colitur date by date, NOT by
the patch tool that produced the earlier eight corrections. That tool compares
colitur's sanctoral data against this repo's calendar ini, so a temporal day
-- computed in code on both sides, in neither file -- is structurally
invisible to it. Its docstring now says so.

TestTemporalEFHolyThursdayColour asserted Good Friday was violet "(unchanged)",
encoding the gap; renamed to TestTemporalEFTriduumColours and updated. A test
asserting the absence of a feature passes for exactly as long as the feature
is absent, which is not the same as being correct. Holy Saturday is still
pinned violet in the other direction, so a careless "the whole Triduum is
black" change fails there.

1 files changed, 18 insertions, 3 deletions

diff --git a/internal/calendar/temporal_ef.go b/internal/calendar/temporal_ef.go
index c649405..3d6c72c 100644
--- a/internal/calendar/temporal_ef.go
+++ b/internal/calendar/temporal_ef.go
@@ -100,12 +100,27 @@ func temporalEF(date time.Time) temporalDay {
 	// Holy Thursday (the Mass of Chrism and the Mass in Cena Domini) is white,
 	// a whole-Mass exception to Passiontide's violet -- RG 128(b)'s own named
 	// exception list, and RG 122 stating the same fact affirmatively in the
-	// White section. Good Friday and Holy Saturday, either side, are NOT
-	// exceptions here (RG 132's black for Good Friday's liturgical action is a
-	// separate, unmodelled gap -- see precedence_ef.go's doc comments).
+	// White section.
 	if sameDay(date, easter.AddDate(0, 0, -3)) {
 		col = White
 	}
+	// Good Friday is BLACK. RG 128(b)'s exception list carries it in the same
+	// sentence as Holy Thursday's -- "...Actione liturgica feria VI in Passione
+	// et Morte Domini usque ad Communionem exclusive..." excepts the day from
+	// Passiontide's violet -- and RG 132 assigns black to it. Adopted
+	// 2026-08-18 from the sibling project colitur, which closed the same gap
+	// against the Missal; this comment previously called it "a separate,
+	// unmodelled gap" and it no longer is.
+	//
+	// The rubric is per-ACTION ("usque ad Communionem exclusive", violet
+	// returns for the Communion rite) and this model carries one colour per
+	// day, so black is the day's principal colour -- the same acknowledged
+	// limit the Palm Sunday blessing already has. missalemeum's own colour set
+	// for the day is "bv", black first, so even the upstream this file is
+	// generated against agrees on the ordering.
+	if sameDay(date, easter.AddDate(0, 0, -2)) {
+		col = Black
+	}
 	sun := date.Weekday() == time.Sunday
 
 	// Major feasts of the Lord (I class): nice titles + colour.