♻️ Extract health bar border color by monster type logic into local function

This eliminates direct array indexing by an enum which allows us to move into enum class without casting.

Source/qol/monhealthbar.cpp

@@ -83,9 +83,24 @@ void DrawMonsterHealthBar(const Surface &out)
 		DrawArt(out, position + Displacement { border + 1, border + 1 }, &health, 0, barProgress, height - (border * 2) - 2);
 	}
 
+	constexpr auto getBorderColor = [](_mc_id monsterClass) {
+		switch (monsterClass) {
+		case MC_UNDEAD:
+			return 248;
+
+		case MC_DEMON:
+			return 232;
+
+		case MC_ANIMAL:
+			return 150;
+
+		default:
+			app_fatal("Invalid monster class '%i'.", monsterClass);
+		}
+	};
+
 	if (sgOptions.Gameplay.bShowMonsterType) {
-		Uint8 borderColors[] = { 248 /*undead*/, 232 /*demon*/, 150 /*beast*/ };
-		Uint8 borderColor = borderColors[monster.MData->mMonstClass];
+		Uint8 borderColor = getBorderColor(monster.MData->mMonstClass);
 		int borderWidth = width - (border * 2);
 		UnsafeDrawHorizontalLine(out, { position.x + border, position.y + border }, borderWidth, borderColor);
 		UnsafeDrawHorizontalLine(out, { position.x + border, position.y + height - border - 1 }, borderWidth, borderColor);