feat(combat): use the cut-out enemy art and scale sprites per monster

Swap the enemy body art for the background-free versions and trim every
sprite to its opaque bounds so the fighters share one ground baseline
instead of floating in a padded box.

Sprite height is now a share of the battlefield rather than a fixed
clamp, set per monster key, so a low-slung rat and a standing bandit keep
believable proportions against the player at any stage size.

apps/web/src/app/shared/monster-artwork.ts

@@ -17,10 +17,23 @@ const COMBAT_MONSTER_ICON: Readonly<Record<string, string>> = {
   'road-bandit': '/images/combat/icons/road-bandit-128.png',
 };
 
+// Share of the battlefield height each monster sprite occupies, so a hulking
+// bandit and a low-slung rat keep believable proportions against the player.
+const COMBAT_MONSTER_SCALE: Readonly<Record<string, number>> = {
+  'ash-rat': 0.46,
+  'road-bandit': 0.82,
+};
+
+const DEFAULT_MONSTER_SCALE = 0.6;
+
 export function combatMonsterSpritePath(monsterKey: string): string | undefined {
   return COMBAT_MONSTER_SPRITE[monsterKey];
 }
 
+export function combatMonsterSpriteScale(monsterKey: string): number {
+  return COMBAT_MONSTER_SCALE[monsterKey] ?? DEFAULT_MONSTER_SCALE;
+}
+
 export function combatMonsterIconPath(monsterKey: string): string | undefined {
   return COMBAT_MONSTER_ICON[monsterKey];
 }