Slightly densify missile smoke trails

Co-authored-by: Codex <codex@openai.com>

airdef-mod/src/smoke.rs

@@ -13,6 +13,8 @@ use std::collections::HashMap;
 
 const MAX_TRAIL: usize = 2400;
 const MAX_TOTAL: usize = 4000;
+// A small optical-density lift for powered missile trails. Keep geometry and budgets unchanged.
+const MISSILE_TRAIL_DENSITY: f32 = 1.12;
 
 struct Trail {
     seg: SmokeSegment,
@@ -135,7 +137,7 @@ fn rocket(scale: f32, density: f32, life: f32) -> Look {
     Look {
         r0: 0.25 * scale,
         r1: 1.2 + 1.6 * scale,
-        density,
+        density: density * MISSILE_TRAIL_DENSITY,
         soot: 0.02,
         clear: 0.8 + 1.2 * scale,
         life: life + 250.0 * scale,
@@ -163,7 +165,7 @@ fn drone_look(class: Class, scale: f32) -> Look {
         Class::Cruise => Look {
             r0: 0.6,
             r1: 3.0,
-            density: 0.6,
+            density: 0.6 * MISSILE_TRAIL_DENSITY,
             soot: 0.3,
             clear: 2.0,
             life: 600.0,