Rework test262-runner.py to support --workers N parallel shards, each running
a long-lived sx_server session. Replace thread-per-readline with a select-based
raw-fd line buffer.
On 2-core machines, 1 worker still beats 2 (OCaml eval is CPU-bound and starves
when shared). Auto-defaults n_workers=1 on <=2 CPU, nproc-1 (up to 8) otherwise.
Throughput baseline: ~1.1 Math tests/s serial on 2-core (unchanged; the
evaluator dominates). The runner framework is now ready to scale on bigger
machines without further code changes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>