Add benchmark suite for alloc/dispatch/collection workloads (jolt-1r86) (#135)

The ray tracer is float-compute-bound (devirt, alloc removal, type-proving all
measured flat on it), so it can't validate the optimization passes. Add a small
cross-language suite (AWFY + CLBG style, portable Clojure) isolating the axes it
misses:

  binary-trees  allocation / GC pressure (escaping short-lived records)
  dispatch      megamorphic protocol dispatch (~1M dispatches/s; WP can't devirt)
  collections   persistent map/vector churn

bench/run.sh runs them; bench/README.md maps each to the pass it exercises.

collections immediately surfaced jolt-684u: the persistent hash map is O(n) per
assoc (flat copy-on-write bucket array, not a HAMT) — n=4000 assocs take 50s.
Invisible to the ray tracer (no maps).

Co-authored-by: Yogthos <yogthos@gmail.com>

bench/run.sh

@@ -0,0 +1,39 @@
+#!/bin/sh
+# Run the jolt benchmark suite and print mean ms per benchmark.
+#
+# Each benchmark isolates an axis the ray tracer (float-compute-bound) doesn't
+# capture — see README.md. Run back-to-back against `main` to measure a pass's
+# impact (the same protocol as test/bench/core-bench.janet).
+#
+#   bench/run.sh                 # default sizes, whole-program optimization on
+#   JOLT_WHOLE_PROGRAM=0 bench/run.sh   # compare with WP off
+#   bench/run.sh binary-trees    # one benchmark
+#
+# Needs `jolt` on PATH (build with `jpm build`; export PATH="$PWD/build:$PATH").
+set -e
+cd "$(dirname "$0")"
+
+export JOLT_DIRECT_LINK="${JOLT_DIRECT_LINK:-1}"
+export JOLT_WHOLE_PROGRAM="${JOLT_WHOLE_PROGRAM:-1}"
+export JOLT_APP_PATHS="$PWD"
+export JOLT_PATH="$PWD"
+
+# name:default-arg  (arg sized to run in a few seconds each)
+# NOTE collections is small because the persistent map is O(n)/assoc (jolt-684u);
+# raise it once that's fixed to a HAMT.
+BENCHES="binary-trees:14 dispatch:2000 collections:1500"
+
+run_one() {
+  ns="${1%%:*}"; arg="${2:-${1##*:}}"
+  printf '%-16s ' "$ns"
+  jolt -m "$ns" "$arg" 2>&1 | awk '/^mean:/{print}'
+}
+
+if [ -n "$1" ]; then
+  for spec in $BENCHES; do
+    [ "${spec%%:*}" = "$1" ] && run_one "$spec" "$2"
+  done
+else
+  echo "jolt benchmark suite (WP=$JOLT_WHOLE_PROGRAM)"
+  for spec in $BENCHES; do run_one "$spec"; done
+fi