Brummel
a1b0ad5723
Closes the structural gap between bench/run.sh (one-shot capture into JOURNAL) and a continuous tripwire. baseline.json records 31 metrics (16 throughput, 15 latency) with per-metric one-sided tolerances tuned to absorb run-to-run noise on a quiet developer machine; check.py spawns run.sh, parses both the throughput pipe-table and the per-arm latency stanzas, diffs against the baseline, prints a per-metric report, and exits non-zero on any regression beyond tolerance. User-facing flags: --from-file, --stdin, --baseline, and --update-baseline (re-run + overwrite baseline.json after intentional improvements). Validation: captured the baseline, then re-ran end-to-end. All 31 metrics within tolerance. The harness also caught a single-capture explicit-rc p99 spike (357.5 us) that was first read as drift vs. yesterday's 18g.tidy.fu2 numbers but came in at 294.6 us on the follow-up run — exactly the kind of noise the tolerance band is there to absorb. Without 21'a we would have either chased a phantom or buried the signal; with it, single noisy runs are data points, not verdicts. Tidy-iter discipline addition (run check.py at every family close alongside the architect drift report) is recommended in JOURNAL but not enacted in this iter — that's an orchestrator-level update to CLAUDE.md.