BenchRepo for isolated concurrency testing against temp DB files.
Correctness tests prove WAL concurrent reads, IMMEDIATE transaction
mode vs DEFERRED upgrade failures, and PRAGMA application. Benchmark
tests (tagged :benchmark, excluded by default) measure throughput.
mix bench.sqlite runs HTTP load scenarios against the full Phoenix
stack with --prod, --scale, --pool-size, and --busy-timeout options.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>