GLD Overlay on GC

Plots GLD levels on GC

• Uses live GLD + live GC during GLD premarket→after-hours (04:00–20:00 NY, Mon–Fri)
  
• Outside that window, it holds the last ratio from the prior daily close
  
• Updates lines after "min_move"
  
• Draws a grid of GLD $1 levels (±N) mapped into GC space