In estimate()'s on_step_changed closure, the new 'pot = step.get("pot", {})'
local variable shadowed the outer 'pot' (Pot plant instance), causing
pot.set_plant_params() to be called on a plain dict and crash on load.
Renamed to 'step_pot' to avoid the collision.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T52JH848ojhXXHn1bAzdC3