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, 34 insertions, 0 deletions

diff --git a/internal/calendar/temporal_ef_test.go b/internal/calendar/temporal_ef_test.go
index 1290a59..e8ef391 100644
--- a/internal/calendar/temporal_ef_test.go
+++ b/internal/calendar/temporal_ef_test.go
@@ -300,3 +300,37 @@ func TestTemporalEFBVMSaturday(t *testing.T) {
 		}
 	}
 }
+
+// TestTemporalEFRogationDays pins RG 87's Minor Litanies: "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) makes them
+// violet, "for the procession and Mass of the Greater and Lesser Litanies" --
+// a penitential note inside white Paschaltide.
+//
+// The Wednesday is asserted in the opposite direction on purpose. Easter+38 is
+// by construction the Vigil of the Ascension, II class, which wins the day; the
+// rubric asks for a COMMEMORATION there, which this function cannot express
+// since it returns one office per day. A change that extended the Rogation
+// branch to +38 to "complete" the rubric would silently displace the Vigil, and
+// this test is what stops it.
+func TestTemporalEFRogationDays(t *testing.T) {
+	// 2027: Easter is 28 March, so the Rogation days are 3-5 May and the
+	// Monday is unimpeded that year.
+	easter := d("2027-03-28")
+	for off, want := range map[int]string{36: "ef-rogation-monday", 37: "ef-rogation-tuesday"} {
+		day := easter.AddDate(0, 0, off)
+		got := temporalEF(day)
+		if got.Cel.Slug != want {
+			t.Errorf("Easter+%d (%s): slug = %q, want %q", off, day.Format("2006-01-02"), got.Cel.Slug, want)
+		}
+		if got.Cel.Colour != Violet {
+			t.Errorf("Easter+%d (%s): colour = %s, want violet (RG 128(d))",
+				off, day.Format("2006-01-02"), got.Cel.Colour)
+		}
+	}
+	// Easter+38 is the Ascension's Vigil and must stay so.
+	if got := temporalEF(easter.AddDate(0, 0, 38)); got.Cel.Slug != "ef-ascension-vigil" {
+		t.Errorf("Easter+38: slug = %q, want ef-ascension-vigil -- the Rogation Wednesday's "+
+			"commemoration cannot be built here without displacing the Vigil", got.Cel.Slug)
+	}
+}