feat: support curated abilities and objective victory

src/Domain/UnitState.php

@@ -112,6 +112,15 @@ final readonly class UnitState
         return $this->copy(health: max(0, $this->health - max(0, $damage)));
     }
 
+    public function restoreHealth(int $amount): self
+    {
+        if ($amount < 0) {
+            throw new InvalidArgumentException('Restore health amount cannot be negative.');
+        }
+
+        return $this->copy(health: min($this->maxHealth, $this->health + $amount));
+    }
+
     public function markAttacked(): self
     {
         return $this->copy(hasAttacked: true);