feat: opencode theme (default)

internal/tui/theme/manager.go

@@ -92,6 +92,11 @@ func AvailableThemes() []string {
 		names = append(names, name)
 	}
 	slices.SortFunc(names, func(a, b string) int {
+		if a == "opencode" {
+			return -1
+		} else if b == "opencode" {
+			return 1
+		}
 		return strings.Compare(a, b)
 	})
 	return names