added lifeline-style

src/renderer.typ

@@ -1,5 +1,5 @@
 #import "@preview/cetz:0.2.2": canvas, draw
-#import "utils.typ": get-participants-i
+#import "utils.typ": get-participants-i, get-style
 #import "group.typ"
 #import "sequence.typ"
 #import "separator.typ"
@@ -209,10 +209,12 @@
 
       // Draw lifeline rectangles (reverse for bottom to top)
       for rect in rects.rev() {
-        let (cx, y0, y1) = rect
+        let (cx, y0, y1, style) = rect
+        let style = get-style("lifeline", style)
         draw.rect(
           (cx - LIFELINE-W / 2, y0),
-          (cx + LIFELINE-W / 2, y1)
+          (cx + LIFELINE-W / 2, y1),
+          ..style
         )
       }