Refactor MonsterAttack() extra melee hit windows without behavior cha…

[morfidon]

Summary

Refactor the family-specific extra melee hit windows in MonsterAttack() into a small helper abstraction.

This patch is intentionally behavior-preserving. It does not change gameplay, timing, or audio behavior. It only makes the existing multi-hit logic easier to read and reason about.

What changed

• added a small MeleeAttackWindow helper struct
• moved the Magma and Storm extra melee hit windows out of inline conditionals in MonsterAttack()
• kept the normal melee hit path separate from the family-specific extra hit windows
• left Snake attack sound timing unchanged

Preserved behavior

This patch is intended to keep the current behavior exactly as it is today:

• the normal melee hit still happens at animFrameNum - 1
• Magma monsters still perform their extra hit on frame 8
• Storm monsters still perform their extra hit on frame 12
• the same hit chance and damage modifiers are still applied for those extra hits
• Snake attack sound timing still happens on frame 0

Why

MonsterAttack() currently mixes three different concerns in one place:

• the default melee attack flow
• family-specific extra hit timing
• special-case sound timing

Pulling the extra hit windows into a clearer abstraction makes the code easier to inspect without changing what the game does. It also gives us a cleaner base for any later discussion about these monster families, without combining that discussion with gameplay changes in this patch.

Non-goals

• no gameplay rebalance
• no attack timing changes
• no audio behavior changes
• no move to monster data tables yet