Cheng 4.48 release (from 2024)

• 9-bit fixed point (16-bit weights and biases), faster inference, new bigger NN, 4 billion selfplay, new topo: 736-576*2-1
• more tactical search at the cost of some elo loss:
  • dropped recapture extensions
  • reenabled fractional plies
  • relaxed singular margin
  • more check extensions in scout nodes
  • SEE pruning
• bench 10044316