feat(ai): 新增 IBossControl facet——Boss 阶段状态经 IAiContext 供图读取

非 Boss 敌人访问 IAiContext.Boss 显式抛 InvalidOperationException，
不返回空对象掩盖小怪图误挂 Boss 边的错误。BossResource 补 IsFull 供图条件边判定。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Assets/Tests/EditMode/Enemies/EnemyBrainContextBossFacetTests.cs

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+using System;
+using NUnit.Framework;
+using UnityEngine;
+using UnityEngine.TestTools;
+using BaseGames.Enemies;
+
+namespace BaseGames.Tests.EditMode.Enemies
+{
+    public class EnemyBrainContextBossFacetTests
+    {
+        // EnemyBase.Awake 会对缺失的碰撞体/引用报错，这些与本测试无关。
+        [SetUp]    public void SetUp()    => LogAssert.ignoreFailingMessages = true;
+        [TearDown] public void TearDown() => LogAssert.ignoreFailingMessages = false;
+
+        static T MakeEnemy<T>(string name) where T : EnemyBase
+        {
+            var go = new GameObject(name);
+            return go.AddComponent<T>();
+        }
+
+        [Test]
+        public void NonBoss_AccessingBossFacet_Throws()
+        {
+            var enemy = MakeEnemy<EnemyBase>("plain-enemy");
+            var ctx   = new EnemyBrainContext(enemy);
+
+            Assert.Throws<InvalidOperationException>(() => { var _ = ctx.Boss; });
+
+            UnityEngine.Object.DestroyImmediate(enemy.gameObject);
+        }
+
+        [Test]
+        public void Boss_AccessingBossFacet_ReturnsTheBoss()
+        {
+            var boss = MakeEnemy<BossBase>("boss");
+            var ctx  = new EnemyBrainContext(boss);
+
+            Assert.AreSame(boss, ctx.Boss);
+            Assert.AreEqual(0, ctx.Boss.CurrentPhase);
+            Assert.IsFalse(ctx.Boss.IsPhaseTransitioning);
+            Assert.IsFalse(ctx.Boss.ResourceFull);   // 未挂 BossResource
+
+            UnityEngine.Object.DestroyImmediate(boss.gameObject);
+        }
+    }
+}

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