Construct a Lucid tensor from any object exposing the DLPack
protocol (__dlpack__) or from a raw PyCapsule.
Memory is shared with ext_tensor where possible (CPU only). The
result lives on CPU regardless of the producer's device — Metal
consumers should .to(device='metal') after the import.
Requires numpy as the canonical DLPack bridge — install via
pip install lucid[numpy] if missing.