Making both arcs 400px (same-size rings, requested for visual alignment)
broke independent dragging: LVGL's adv_hittest arc hit test only accepts
touches within an arc's own ring band (radius - arc_width to radius, within
its angular span), confirmed via lv_arc.c LV_EVENT_HIT_TEST. Two identical
rings occupy the same band, so only the topmost (cool_arc) ever won the
touch, confirmed on hardware. Reverting to 400px/360px nested rings restores
independent heat/cool dragging; same-size same-position arcs are not
achievable with LVGL's current hit-testing without a larger redesign.
pyr0ball
c9df881066