Chez numeric tower: exact ints / Ratio / double for JVM parity (jolt-n6al)

jolt was all-flonum (one :number type, inherited from Janet whose only number
type is a double). The Chez runtime has a full numeric tower, so the zero-Janet
path now carries it = JVM Clojure semantics:

  (/ 1 2)      => 1/2      (exact Ratio, was 0.5)
  (integer? 3) => true   (integer? 3.0) => false   (float? 3.0) => true
  (ratio? (/ 1 2)) => true   (= 3 3.0) => false   (== 3 3.0) => true
  (+ 1 2) => 3 (exact)   (/ 1.0 2) => 0.5 (double)

jolt= was already exactness-aware (values.ss) and == is value-equality, so
=/== match the JVM split. The reader preserves exactness (integer literals exact,
a/b ratios exact rationals, decimals/exponents flonums); backend_scheme emit-const
renders exact ints/ratios and flonums faithfully; the value-position arithmetic,
count, int, compare, bit ops, parseLong, string .length/.indexOf, range,
timestamps, and array bytes return exact integers (= JVM int/long) instead of
coercing to flonum. double/parseDouble/clojure.math floor|ceil|signum stay double.

Only the zero-Janet path carries the tower (the Janet reader loses exactness into
a double before emit). The prelude/all-flonum path is unaffected for compiled code;
the runtime reader is shared, so a couple of all-flonum reader assertions become
value (==) assertions. ~16 numeric corpus cases now give the JVM tower value vs the
Janet-era :expected and are allowlisted as tower divergences (Chez == reference
JVM) pending the corpus flip to JVM (jolt-ecz0). No BigDecimal type (1M).

Re-minted. zero-janet 2682 (floor 2698->2682, the reclassified tower cases), 0 new
divergences; fixpoint 10/10, bootstrap 6/6, spine 35/35, cli 49/49; Janet gate 155
files 0 failed.

host/chez/math.ss

@@ -22,7 +22,8 @@
       (- (expt (- x) (/ 1.0 3.0)))
       (expt x (/ 1.0 3.0))))
 
-(define (jolt-math-round x) (floor (+ x 0.5)))
+;; clojure.math/round returns a long (exact); floor/ceil/signum/rint return doubles.
+(define (jolt-math-round x) (exact (floor (+ x 0.5))))
 (define (jolt-math-signum x) (cond ((< x 0.0) -1.0) ((> x 0.0) 1.0) (else 0.0)))
 (define (jolt-math-to-degrees r) (/ (* r 180.0) jolt-math-pi))
 (define (jolt-math-to-radians d) (/ (* d jolt-math-pi) 180.0))