feat(api): let monsters raise a breakable defensive guard

apps/api/src/monsters/monster-abilities.ts

@@ -26,9 +26,22 @@ export interface MonsterBleedAbility {
   durationRounds: number;
 }
 
+export interface MonsterGuardAbility {
+  /**
+   * The monster forgoes its attack on every round divisible by this and
+   * covers instead, raising its armor for `durationRounds`. SHIELD_BASH
+   * breaks it, the same answer the telegraph already taught (Playable Slice
+   * 0.10 §5).
+   */
+  roundInterval: number;
+  armorBonus: number;
+  durationRounds: number;
+}
+
 export interface MonsterAbilities {
   telegraph?: MonsterTelegraphAbility;
   bleed?: MonsterBleedAbility;
+  guard?: MonsterGuardAbility;
 }
 
 export const NO_MONSTER_ABILITIES: MonsterAbilities = {};