oracle_ef_test: three structural coverage gaps in the strengthened test

Cheap fixes flagged in review, all confirmed against the committed
snapshot before being applied:

1. An unmapped season phrase skipped the RANK AND COLOUR checks too,
   not just the season comparison -- `continue` in the wrong place.
   Confirmed live: neither Holy Thursday ("maundy"/"holy week" do
   not match the title "Holy Thursday" itself) nor any of the six
   September Ember days (no "ember" case exists at all; the Advent
   and Lent Ember days only ever passed by an incidental substring
   match on "advent"/"lent") had any oracle coverage at all --
   reverting the Holy Thursday colour fix left this test green.
   Season skip and rank/colour checks are now independent.

2. Colour membership alone cannot catch a Rose regression: violet is
   a member of every rose/violet pair by construction (Gaudete/
   Laetare), so "got violet, want one of [rose violet]" passed even
   with RG 131's Rose support removed entirely. On the day the pair
   actually names (oracle rank 1, the Sunday itself, not a weekday
   reusing its propers), a colour set containing rose now demands
   rose specifically.

3. `has("sexagesima")` never matched missalemeum's own ligatured
   "Sexagesimæ" -- confirmed in the committed snapshot: the ligatured
   form appears 10 times, the unligatured form only 4, and every
   ligatured instance mapped to season "" (skipped from ALL coverage,
   not merely a season miss, given finding 1 above). Normalised once,
   generally (æ -> ae), not as a single hardcoded word, so any other
   ligature this generator's own data may carry is covered too.

Net effect on TestOracleEF: 730 checked (up from 691), 29 skipped
(down from 39) -- the 10 reclaimed by fix 3. Still green: 0
unallow-listed rank or colour mismatches over the full snapshot.

1 files changed, 38 insertions, 5 deletions

diff --git a/internal/calendar/oracle_ef_test.go b/internal/calendar/oracle_ef_test.go
index 7a1b61e..6d63220 100644
--- a/internal/calendar/oracle_ef_test.go
+++ b/internal/calendar/oracle_ef_test.go
@@ -68,6 +68,14 @@ var efRankNumbers = map[int]calendar.Rank{
 // there, not to Time after Epiphany.
 func efSeasonFromString(s string, month int) calendar.Season {
 	s = strings.ToLower(s)
+	// missalemeum's own EN-locale text still carries the occasional Latin
+	// ligature (e.g. "Feria V after Sexagesimæ") -- confirmed in the
+	// committed snapshot: "Sexagesimæ" appears 10 times, "Sexagesima" (no
+	// ligature) only 4, and the ligatured form matched no case below,
+	// silently mapping those 10 days to season "" (skipped from coverage
+	// entirely, not merely a season miss). Normalising here fixes every
+	// current and future ligature in one place, not just this one word.
+	s = strings.ReplaceAll(s, "æ", "ae")
 	has := func(subs ...string) bool {
 		for _, sub := range subs {
 			if strings.Contains(s, sub) {
@@ -242,14 +250,22 @@ func TestOracleEF(t *testing.T) {
 		}
 		day, _ := time.Parse("2006-01-02", date)
 		want := efSeasonFromString(src, int(day.Month()))
-		if want == "" {
-			skipped++
-			continue
-		}
 		total++
 		got := calendar.Compute(day.UTC(), sel, layers)
 
-		if got.Season != want {
+		// An unrecognised season phrase skips the SEASON comparison only --
+		// it must not also skip Rank/Colour for that day. A `continue` here
+		// once did exactly that, silently zeroing oracle coverage for every
+		// day whose phrase efSeasonFromString doesn't recognise (Holy
+		// Thursday -- "maundy"/"holy week" don't match "Holy Thursday"
+		// itself; the six September Ember days -- no "ember" case exists at
+		// all, only Advent/Lent Ember days pass by an incidental substring
+		// match on "advent"/"lent"). Reverting the Holy Thursday colour fix
+		// (temporal_ef.go) left this test green under the old `continue`;
+		// it does not under this one.
+		if want == "" {
+			skipped++
+		} else if got.Season != want {
 			seasonMiss++
 			if shownSeason < 40 {
 				t.Errorf("%s: EF season got %q want %q (from %q)", date, got.Season, want, src)
@@ -279,6 +295,23 @@ func TestOracleEF(t *testing.T) {
 				break
 			}
 		}
+		// Membership alone cannot catch a Rose regression: violet is a
+		// member of every rose/violet pair by construction (Gaudete/
+		// Laetare), so "got violet, want one of [rose violet]" passes even
+		// if RG 131's Rose support (temporal_ef.go) were reverted entirely.
+		// On the day the rose/violet pair actually names -- oracle rank 1,
+		// the Sunday itself, not a weekday reusing its propers (which
+		// carries a lower rank and is deliberately membership-only, this
+		// file's own doc comment item 3) -- a colour set containing rose
+		// demands rose specifically, not merely "some member".
+		if colourOK && od.Rank == 1 && got.Colour != calendar.Rose {
+			for _, c := range od.Colours {
+				if c == "p" {
+					colourOK = false
+					break
+				}
+			}
+		}
 		if !colourOK && len(od.Colours) > 0 {
 			if ok, reason := efAllowed(date, day, od, "colour"); ok {
 				colourAllowed++