We've got enemies and movement!!

Assets/_Project/Scripts/Gameplay/LevelLoader.cs

@@ -365,6 +365,14 @@ namespace TD.Gameplay
         // NetworkObject spawns and its Start/OnNetworkSpawn stamps its own
         // footprint locally.
 
+        /// <summary>
+        /// Fired on every peer whenever <see cref="SetWalkable"/> changes a tile's
+        /// walkability. <see cref="TD.Gameplay.PathfindingService"/> subscribes to
+        /// invalidate cached paths so in-flight enemies reroute after a tower is
+        /// placed or removed.
+        /// </summary>
+        public event System.Action OnWalkabilityChanged;
+
         /// <summary>
         /// Sets the runtime walkability of <paramref name="tile"/>. Called by
         /// <c>TowerPlacementManager</c> on the server when a tower is accepted (pass
@@ -374,7 +382,9 @@ namespace TD.Gameplay
         public void SetWalkable(Vector2Int tile, bool walkable)
         {
             if (!TryFlatIndex(tile, out int idx)) return;
+            if (runtimeWalkability[idx] == walkable) return; // no change — don't fire event
             runtimeWalkability[idx] = walkable;
+            OnWalkabilityChanged?.Invoke();
         }
 
         /// <summary>