Initial Combat Implementation

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

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+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.NetCode;
+
+namespace ProjectM.Simulation
+{
+    /// <summary>
+    /// Ghost component on the projectile prefab. Drives predicted+server movement and carries the
+    /// classification key used to reconcile a client's predicted-spawned projectile with the server's
+    /// authoritative ghost. <see cref="Direction"/> is replicated so the server's auto-targeted aim
+    /// reconciles the client's raw-aim prediction; <see cref="SpawnId"/> is replicated so it lives in
+    /// snapshot history for the predicted-spawn classifier. Speed/Damage/Range are baked on the prefab
+    /// (identical both worlds → deterministic) and not replicated; DistanceTravelled is integrated
+    /// locally each tick and not replicated.
+    /// </summary>
+    public struct Projectile : IComponentData
+    {
+        /// <summary>Planar XZ travel direction (world XZ mapped to float2 x,y), normalized.</summary>
+        [GhostField(Quantization = 1000)] public float2 Direction;
+
+        /// <summary>
+        /// Classification key: (ownerNetId << 16) | absoluteFireCount. Replicated so it is present
+        /// in snapshot history; the client classifier matches this against its predicted spawn.
+        /// </summary>
+        [GhostField] public uint SpawnId;
+
+        /// <summary>Travel speed in units/second. Baked on the prefab; not replicated.</summary>
+        public float Speed;
+
+        /// <summary>Damage applied on hit. Baked on the prefab; not replicated.</summary>
+        public float Damage;
+
+        /// <summary>Max travel distance before the server expires the projectile. Baked on the prefab; not replicated.</summary>
+        public float Range;
+
+        /// <summary>Integrated distance travelled (predicted on client + authoritative on server). Not replicated.</summary>
+        public float DistanceTravelled;
+    }
+}