Feature: @mirror Everywhere

### For which plugin is the feature?

FancyNpcs

### Describe your idea

Please add @mirror tag in every command such as:
/npc equipment set mainhand @mirror - Mirrors every item the player is holding.

/npc attribute mirror set pose @mirror - Mirrors the player's pose, such as sneaking when the player sneaks, jumping when the player jumps, etc.

Also add something to mirrors the player's attacks, such as left-clicking when the player left-clicks.

Start by tracing the FancyNpcs command paths shown in the examples: `/npc equipment` and `/npc attribute mirror`. Define the scope of `@mirror`, including held items, pose changes, and player attacks, then verify each requested command behavior in a Minecraft test setup. Done means the supported commands mirror the corresponding player actions consistently.

Written by the indexing model from the issue text.