test(cog-pose): cross-language adapter integration (Python producer -> Rust engine)

Closes the last verification gap in the calibration feature: previously the
Python producer and Rust consumer were proven compatible only by format
matching. Now a real ~11KB adapter fitted by cog_calibrate.py on the in-repo
pose_v1.safetensors is committed as a fixture, and a Rust test loads it via
the engine and asserts is_calibrated() + that it changes inference output.
The full Python->Rust calibration contract is verified with a real artifact.
7/7 cog-pose tests pass.

Co-Authored-By: claude-flow <ruv@ruv.net>