Make the benchmark harness build optimized binaries on Chez (#220)

bench/run.sh was Janet-era: it invoked a 'jolt' binary and set
JOLT_DIRECT_LINK/JOLT_WHOLE_PROGRAM, none of which exist on Chez, where
'joltc run -m' runs fully unoptimized (direct-link and inline default off). So
the suite was measuring jolt's unoptimized path.

run.sh now compiles each benchmark to an optimized AOT binary (joltc build
--direct-link --opt) and times it against JVM Clojure on the same portable
source, auto-detecting the Chez kernel dev files like build-smoke.sh. Adds
bench/deps.edn so joltc resolves the namespaces, NO_JVM to skip the reference.

mandelbrot.clj dropped its jolt.png require so the JVM reference can run it; the
picture demo moved to mandelbrot_png.clj (jolt-only). README scorecard refreshed
with current Chez numbers and the two-regime read (compute ~8-10x substrate floor;
dispatch/alloc ~120-330x architectural gaps the passes don't touch). Stale
'jolt -m' header lines point at bench/run.sh.

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

bench/collections.clj

@@ -5,7 +5,7 @@
 ;; records, no collections in the hot loop) doesn't touch.
 ;;
 ;; Portable Clojure (jolt + JVM Clojure).
-;;   jolt -m collections 200000     (JOLT_DIRECT_LINK=1 JOLT_WHOLE_PROGRAM=1)
+;;   bench/run.sh collections 200000
 (ns collections)
 
 ;; map churn: accumulate a frequency map over a stream of keys, then sum it back