feat(ef): Rogation Monday and Tuesday (RG 87)

RG 87: "Litaniae minores seu Rogationes, per se, assignantur feriis II, III et
IV ante festum Ascensionis Domini." Easter+36 and +37 are that Monday and
Tuesday. RG 128(d) gives them violet -- "for the procession and Mass of the
Greater and Lesser Litanies" -- a penitential note inside white Paschaltide.
lectio computed no Rogation days at all and showed a plain paschaltide feria.

The WEDNESDAY is deliberately not built, and the test asserts its absence.
Easter+38 is by construction the Vigil of the Ascension, II class, which wins
the day outright; what the rubric asks for there is a COMMEMORATION, and this
function returns one office per day. colitur reaches it through a movable-date
entry in its sanctoral overlay. Extending the Rogation branch to +38 to
"complete" the rubric would silently displace the Vigil, so the test pins the
Vigil rather than leaving the omission to a comment.

Rank is left as the feria's: these are IV-class days and any III-class saint
displaces them, which is what makes the office rare. In 2026 all three are
impeded and none appears; 2027 has the Monday unimpeded, and lectio and
colitur are byte-identical across 2-5 May that year.

One oracle allow-list entry: missalemeum builds no Rogation days either and
shows a white feria, so it is the outlier here rather than lectio.

1 files changed, 25 insertions, 0 deletions

diff --git a/internal/calendar/temporal_ef.go b/internal/calendar/temporal_ef.go
index 7d31b8b..a043179 100644
--- a/internal/calendar/temporal_ef.go
+++ b/internal/calendar/temporal_ef.go
@@ -276,6 +276,31 @@ func temporalEF(date time.Time) temporalDay {
 	// Unique ferial slug (season-week-weekday) so proper ferias (Lent, Advent,
 	// Holy Week, Ember days) can key their own readings; green-season ferias
 	// simply have no lectionary entry and fall back to the Sunday.
+	// RG 87: "Litaniae minores seu Rogationes, per se, assignantur feriis II,
+	// III et IV ante festum Ascensionis Domini" -- the Minor Litanies are
+	// assigned to the Monday, Tuesday and Wednesday before the Ascension.
+	// Easter+36 and +37 are that Monday and Tuesday; their colour is violet,
+	// RG 128(d) giving violet "for the procession and Mass of the Greater and
+	// Lesser Litanies", a penitential note inside white Paschaltide.
+	//
+	// The WEDNESDAY is deliberately absent. Easter+38 is by construction the
+	// Vigil of the Ascension, which is II class and wins the day outright, so
+	// there is no Rogation OFFICE to build there -- what the rubric asks for on
+	// that day is a commemoration, and that needs a channel this function does
+	// not have (it returns one office per day). colitur reaches it through a
+	// movable-date entry in its own sanctoral overlay; here it stays unbuilt
+	// rather than half-built, which is why this comment says so.
+	//
+	// The rank is left as the feria's: these are IV-class days per annum and
+	// any III-class saint displaces them, which is what makes the office rare
+	// -- in 2026 all three are impeded and none appears at all.
+	if rog := daysBetween(easter, date); rog == 36 || rog == 37 {
+		slug := "ef-rogation-monday"
+		if rog == 37 {
+			slug = "ef-rogation-tuesday"
+		}
+		return efCel(season, slug, Violet, rank, week)
+	}
 	// RG 78 (Caput IX, "De sancta Maria in sabbato"): "In sabbatis, in quibus
 	// occurrit Officium de feria IV classis, fit de sancta Maria in sabbato."
 	// On a Saturday whose office would otherwise be a IV-class feria, the