Vendored copy of CANON:
  lygo-protocol-stack/protocol0_byte_entropy_filter/src/python/byte_entropy_filter.py

This copy exists so the stream runtime (U:\LYGO\projects\lygo-llm) can fail-closed
on P0 physics without a protocol-stack checkout. If LYGO_STACK_ROOT is set and
the CANON file imports, that overlay wins; on ImportError this vendor is used.

Do not "improve" entropy math here — change CANON first, then recopy.
