feat: read N/M/ratio/radix/exponent number literals; clean suite measurement

Reader gaps caused the clojure-test-suite worker to crash whole deftests on
literals it could not parse (0N, 1.5M, 2r1010, 1/2), losing every assertion in
the file. read-number now handles:
- N (bigint) / M (bigdec) suffixes -> plain number (Jolt has no bignum/bigdec)
- ratios a/b -> double quotient
- radix integers NrDDD (2r1010, 16rFF, 36rZ) parsed by base
- exponents (1e3, 1.5e-2) and 0X hex

Also fixed suite measurement: when-var-exists now skips silently (its SKIP
print to stdout was corrupting the worker's count line, dropping whole files),
and the worker emits counts on an @@COUNTS sentinel line (robust against test
bodies that print, e.g. with-out-str). Runner parses the sentinel; deftest
crashes now report the underlying message.

Impact: clojure-test-suite 210->231 files run, pass 1955->3535, clean files
24->39. Baseline raised to 3450/38.

spec: numbers/literal-syntax (13 cases). jpm test green.

test/integration/suite-worker.janet

@@ -37,4 +37,10 @@
   (def p (eval-string ctx "(clojure.test/n-pass)"))
   (def f (eval-string ctx "(clojure.test/n-fail)"))
   (def e (eval-string ctx "(clojure.test/n-error)"))
-  (printf "%d %d %d" (if (number? p) p 0) (if (number? f) f 0) (if (number? e) e 0)))
+  # A "dump" 2nd arg (or SUITE_DUMP env) also prints each failure/error message
+  # (one DUMP line each) for triage.
+  (when (or (os/getenv "SUITE_DUMP") (= "dump" (get (dyn :args) 2)))
+    (eval-string ctx "(doseq [m (clojure.test/failures)] (println (str \"DUMP \" m)))"))
+  # Counts on a sentinel line so parsers find it even if a test body printed to
+  # stdout (e.g. with-out-str / println-str tests).
+  (printf "@@COUNTS %d %d %d" (if (number? p) p 0) (if (number? f) f 0) (if (number? e) e 0)))