benches: add SMARM_BENCH_SETS (default 5) for stable medians

Each run_n call now collects ITERS × SETS raw samples across all sets
(one warmup before the first set, discarded), then takes a single global
median. Previously only ITERS=15 samples were taken per bench invocation,
which produced noisy results in sweep.py regress.

SMARM_BENCH_SETS is read from the environment; the default of 5 gives
75 samples per bench row (5×15), matching the stability of the multi-run
bash approach without requiring multiple cargo bench invocations.

Also moves scripts/bench_rq.sh into benches/ alongside sweep.py.
The cd "$(dirname "$0")/.." path logic is unchanged.

benches/bench_rq.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+# Run-queue shootout driver (ROADMAP_v0.5 phase 4; RFC 005 slot dimension
+# added for the v0.9 slot shootout).
+#
+# Rebuilds the runtime bench once per rq-* feature and runs the raw-structure
+# microbench once (it covers all structures in a single binary). The RFC 005
+# wake slot is a runtime Config knob, NOT a feature — each rq_runtime binary
+# sweeps slot off/on internally (SMARM_BENCH_SLOT, default "0 1"). Results
+# land in bench_results/ as full logs; the RQCSV lines are aggregated into
+# bench_results/summary.csv and the RQSLOT counter lines (slot hits /
+# displacements, slot-on configs only) into bench_results/slot_counters.csv.
+#
+# Tune the sweep for the box, e.g. on the 20-core machine:
+#   SMARM_BENCH_THREADS="1 2 4 8 16 20" ./scripts/bench_rq.sh
+# Slot-only re-run against the frozen rq-mutex substrate:
+#   SMARM_BENCH_SLOT="0 1" cargo bench --bench rq_runtime
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+OUT=bench_results
+mkdir -p "$OUT"
+: "${SMARM_BENCH_THREADS:=1 2 4}"
+: "${SMARM_BENCH_SLOT:=0 1}"
+export SMARM_BENCH_THREADS SMARM_BENCH_SLOT
+
+echo "== raw structures (one binary, all variants) =="
+cargo bench --bench rq_micro 2>&1 | tee "$OUT/micro.txt"
+
+for v in rq-mutex rq-mpmc rq-striped; do
+  echo "== runtime benches: $v (slot sweep: $SMARM_BENCH_SLOT) =="
+  cargo bench --bench rq_runtime --no-default-features --features "$v" \
+    2>&1 | tee "$OUT/runtime-$v.txt"
+done
+
+# runtime rows: kind,variant,slot,bench,threads,work,median_us,ops_per_s
+# micro rows:   kind,structure,threads,p:c,items,median_us,items_per_s (one
+#               column narrower, as before — split on kind when plotting)
+echo "kind,a,b,c,d,e,median_us,ops_per_s" > "$OUT/summary.csv"
+grep -h '^RQCSV,' "$OUT"/*.txt | sed 's/^RQCSV,//' >> "$OUT/summary.csv"
+
+echo "variant,bench,threads,slot_hits,slot_displacements" > "$OUT/slot_counters.csv"
+grep -h '^RQSLOT,' "$OUT"/*.txt | sed 's/^RQSLOT,//' >> "$OUT/slot_counters.csv" || true
+
+echo
+echo "Summary: $OUT/summary.csv ($(($(wc -l < "$OUT/summary.csv") - 1)) rows)"
+echo "Slot counters: $OUT/slot_counters.csv ($(($(wc -l < "$OUT/slot_counters.csv") - 1)) rows)"