Adding major combat changes and features

Assets/_Project/Scripts/Gameplay/EnemyHealth.cs

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+// Assets/_Project/Scripts/Gameplay/EnemyHealth.cs
+using Unity.Netcode;
+using UnityEngine;
+using TD.Core;
+
+namespace TD.Gameplay
+{
+    /// <summary>
+    /// Per-enemy HP component. Holds replicated HP and is the single point
+    /// through which all damage flows, so resistance lookups (Phase 1.5+) can
+    /// be added in one place without touching every damage source.
+    /// </summary>
+    /// <remarks>
+    /// Lives on the enemy prefab root alongside <see cref="EnemyStatus"/> and the
+    /// future <c>EnemyMovement</c> component (Phase 1.5/1.6). HP is server-written
+    /// and replicated to all clients so health bars can render on any peer.
+    ///
+    /// <b>Death flow (server-only):</b>
+    /// <c>TakeDamage</c> clamps HP to 0, fires <see cref="OnDied"/>, then calls
+    /// <c>NetworkObject.Despawn</c>. Subscribers must not touch the NetworkObject
+    /// after <c>OnDied</c> returns.
+    /// </remarks>
+    [RequireComponent(typeof(NetworkObject))]
+    public class EnemyHealth : NetworkBehaviour
+    {
+        [SerializeField] private float maxHp = 100f;
+
+        private readonly NetworkVariable<float> hp = new NetworkVariable<float>(
+            0f,
+            NetworkVariableReadPermission.Everyone,
+            NetworkVariableWritePermission.Server);
+
+        // ----- Public state -----------------------------------------------
+
+        public float CurrentHp => hp.Value;
+        public float MaxHp     => maxHp;
+        public bool  IsDead    => hp.Value <= 0f;
+
+        // Stub: set by EnemyMovement or spawner in Phase 1.5/1.6.
+        // TowerCombat reads this to honour the GroundedOnly tower flag.
+        public bool IsFlying => false;
+
+        // ----- Events -----------------------------------------------------
+
+        /// <summary>
+        /// Fired on the server immediately before the enemy NetworkObject is despawned.
+        /// <see cref="TD.Combat.TowerCombat"/> subscribes to clear its target reference.
+        /// Do not access the NetworkObject after this event returns.
+        /// </summary>
+        public event System.Action<EnemyHealth> OnDied;
+
+        // ----- NGO lifecycle ----------------------------------------------
+
+        public override void OnNetworkSpawn()
+        {
+            if (IsServer)
+                hp.Value = maxHp;
+        }
+
+        // ----- Server API -------------------------------------------------
+
+        /// <summary>
+        /// Applies <paramref name="damage"/> to this enemy. Server-only; no-op on clients.
+        /// <paramref name="type"/> is recorded for future resistance/weakness lookups —
+        /// all damage is full-value until the resistance table is implemented (Phase 1.5+).
+        /// </summary>
+        public void TakeDamage(float damage, DamageType type)
+        {
+            if (!IsServer) return;
+            if (IsDead)    return;
+
+            // STUB — resistance table slot:
+            // float modified = ResistanceTable.Apply(damage, type, this);
+            float modified = damage;
+
+            hp.Value = Mathf.Max(0f, hp.Value - modified);
+
+            if (hp.Value <= 0f)
+                HandleDeath();
+        }
+
+        // ----- Private ----------------------------------------------------
+
+        private void HandleDeath()
+        {
+            OnDied?.Invoke(this);
+            NetworkObject.Despawn();
+        }
+    }
+}