Initial Combat Implementation

Assets/_Project/Scripts/Simulation/Combat/ProjectileMoveSystem.cs

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+using Unity.Burst;
+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.NetCode;
+using Unity.Transforms;
+
+namespace ProjectM.Simulation
+{
+    /// <summary>
+    /// Predicted projectile integrator: advances every live <see cref="Projectile"/> along its
+    /// replicated planar (XZ) <see cref="Projectile.Direction"/> at its baked <see cref="Projectile.Speed"/>,
+    /// accumulating <see cref="Projectile.DistanceTravelled"/>. Runs inside the prediction loop on the
+    /// owning client (re-simulated on rollback) and once per tick on the server, after
+    /// <see cref="AbilityFireSystem"/> has spawned this tick's shots; filtered to <see cref="Simulate"/>
+    /// so only predicted ghosts move. Deterministic by construction: uses <c>SystemAPI.Time.DeltaTime</c>
+    /// (the fixed tick step) only — no wall-clock, no <c>System.Random</c>. Pure motion: range expiry and
+    /// destruction are server-authoritative in <c>ProjectileDamageSystem</c>, so this system never
+    /// performs structural changes and is fully idempotent across rollback re-simulation.
+    /// </summary>
+    [UpdateInGroup(typeof(PredictedSimulationSystemGroup))]
+    [UpdateAfter(typeof(AbilityFireSystem))]
+    [BurstCompile]
+    public partial struct ProjectileMoveSystem : ISystem
+    {
+        [BurstCompile]
+        public void OnUpdate(ref SystemState state)
+        {
+            float dt = SystemAPI.Time.DeltaTime;
+
+            foreach (var (transform, projectile) in
+                     SystemAPI.Query<RefRW<LocalTransform>, RefRW<Projectile>>()
+                         .WithAll<Simulate>())
+            {
+                float step = projectile.ValueRO.Speed * dt;
+                float3 dir = new float3(projectile.ValueRO.Direction.x, 0f, projectile.ValueRO.Direction.y);
+
+                transform.ValueRW.Position += dir * step;
+                projectile.ValueRW.DistanceTravelled += step;
+            }
+        }
+    }
+}