Adds Part B (peak RSS for K concurrent decodes) to bench_pool_concurrency and
records the findings in benches/POOL-CONCURRENCY.md.
Honest result: under a 2-core quota the thumbnail decode pool shows flat
throughput, p99, AND peak RSS (137 MiB) from K=1..16 — shrink-on-load already
made each decode RAM-cheap, so over-permitting costs nothing measurable here.
The effective_parallelism() migration is therefore a correctness/consistency
change with no downside, mainly protecting the transcode + ffmpeg pools (and
extreme host-core/quota ratios) this box can't reproduce — not a throughput win.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JG5yYZ9s868mJwqT2Qz7ez
Claude