Add AO screening benchmarks

[Jens (JensWehner)]

Summary

• Add an isolated-worker AO-screening benchmark runner covering:
  • CPU dense evaluation
  • CPU screened evaluation
  • GPU evaluation
  • runtime and peak-memory measurements
  • an alkane size ladder
  • resumable, versioned JSON results
  • smoke and preflight-only modes
• Add a rotation benchmark for measuring grid-orientation sensitivity.
• Add clean analysis notebooks for scaling and rotation results.
• Ignore generated benchmark result files.

Generated results and unrelated VXC precision experiments are not included.