make ships orbit their targets

src/lib/config/WorldConfig.h

@@ -49,6 +49,8 @@ struct WorldConfig
     double beltSpeed_tps;               // REQ-GW-BELT-SPEED (tiles/s, converted from m/s in config)
     int tunnelMaxDistance_tiles;        // REQ-BLD-TUNNEL-PAIR
     double departureIntervalSeconds;    // REQ-SHP-RALLY
+    double orbitFactor;                 // REQ-SHP-ORBIT (multiplies tool range for orbit radius)
+    double rallyOrbitRadius_tiles;      // REQ-SHP-ORBIT (fixed orbit radius around the rally point)
 
     WorldRegions regions;
     WorldExpansion expansion;