make ships orbit their targets

src/lib/ecs/component/SalvageScrapBehavior.h

@@ -10,5 +10,6 @@ struct SalvageScrapBehavior
 {
     std::optional<QVector2D> scrapTarget;
     float                    maxCollectionRange_tiles = 0.0f;
+    float                    orbitRadius_tiles = 0.0f;  // REQ-SHP-ORBIT
     float                    score = 0.0f;
 };