collect_cpu now returns (aggregate, [per_core]) and build_sample takes a
rate-state dict, so the pre-existing tests that asserted the old float
return / no-state signature needed updating. Mocks the new collectors
(temps/psi/net/diskio) for determinism.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen