KOPR R22 performance and platform reference

Fixed automatic limits
- Masterdark/masterflat median: maximum 4 threads, one shared 192 MiB allowance.
- Prepared master cache: two recent pairs, 768 MiB hard ceiling and 25% available RAM.
- LIGHT calibration: maximum 2 threads, adaptive per-image RAM estimate.
- Row reprojection: maximum 2 threads, one shared 256 MiB allowance.
- Sigma clipping: maximum 2 threads, one shared 256 MiB allowance.
- Astrometry.net batch: maximum 2 external solve-field processes, isolated work directories.

The user cannot modify these values. Every subsystem has a serial fallback for small jobs, one-CPU systems, insufficient RAM or scheduler initialization failure. Numerical scheduling uses threads rather than Python worker processes.

Release validation
python3 validate_performance_release.py
python3 validate_performance_release.py --json

R22 release evidence
- 680 passed, 3 skipped; 683 tests collected.
- clean-ZIP smoke: 87 passed; release validator PASS; compileall PASS.
- 143 manifest entries; 144 distributable files including manifest.
- archive SHA-256: ef499b399d145c9ea6027170cb1424497ed736ca22b1de9792baa28782120475

Target-machine checks remain required for real Linux/Windows GUI execution, real Astrometry.net and a two-process Windows/WSL solve/cancel cycle.