Calendar: one scrolling list that loads more days at either end

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/ui/calendar_test.go

@@ -124,3 +124,21 @@ func TestSortEntriesAndDayLabel(t *testing.T) {
 		}
 	}
 }
+
+func TestMergeEntries(t *testing.T) {
+	d1, d2, d3 := day(2026, 10, 21), day(2026, 10, 22), day(2026, 10, 23)
+	have := []calEntry{{day: d2, title: "b", episodeID: 2}, {day: d3, title: "c", episodeID: 3}}
+	add := []calEntry{
+		{day: d1, title: "a", episodeID: 1},
+		{day: d2, title: "b", episodeID: 2}, // already there: not duplicated
+		{day: d3, title: "film", movie: true, movieID: 7, sub: "In cinemas"},
+	}
+	got := mergeEntries(have, add)
+	var titles []string
+	for _, e := range got {
+		titles = append(titles, e.title)
+	}
+	if strings.Join(titles, ",") != "a,b,c,film" {
+		t.Errorf("merged = %v", titles)
+	}
+}