tc_constants.py only held States and DEFAULT_THRESHOLDS, both used exclusively by temp_controller_base.py and its subclasses; fold them into temp_controller_base.py directly and drop the now-empty module. Also drop heat_diffusion.py, unused since pot.py switched to the delay-line model, and the matching dead import in pot.py. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>