ItemParticleAttachment

Particles for a held item's Bedrock attachable. A producer plugin (FreeMinecraftModels) writes assets/<namespace>/rspm_item_particles/<model path>.json beside the Java item model: effect short names mapped to particle identifiers it ships in its Bedrock bundle, locators in Java item model pixels, and a looping particle timeline. This adds the locators to the item geometry, writes the timeline as an attachable animation, and wires both into the attachable, so the Bedrock client draws the particles at the real hand in first and third person.