Load the TSL / WebGPU material cone, fetching its chunk on first call.
Idempotent and concurrency-safe: repeat calls return the cached registry (or join the in-flight load) rather than re-importing.
Load the TSL / WebGPU material cone, fetching its chunk on first call.
Idempotent and concurrency-safe: repeat calls return the cached registry (or join the in-flight load) rather than re-importing.