Chez Phase 2 (inc L): var def-time metadata (jolt-zikh)

Capture a def's reader metadata on the Chez var. The :def emit now lowers a def
with non-empty metadata to def-var-with-meta!, which stores the user meta
(^:private / ^Type tag / docstring -> {:doc}) in an eq side-table keyed by the
var-cell. jolt-meta of a var-cell merges that onto {:ns :name} derived from the
cell, so every var reports {:ns :name} like Clojure with the def-time meta
layered on. (^{:map} metadata on a def name stays uncompilable for the compiler
generally — analyzer rejects it, the Janet back end punts to its interpreter,
which Chez lacks — so it's out of subset, not a meta-capture gap.)

Added natives-meta.ss to the prelude-cache fingerprint. Prelude parity
1969 -> 1972, 0 new divergences; the three var-metadata allowlist entries
(^:private / ^Type tag / docstring) dropped. New focused gate
test/chez/_var_meta.janet.

host/chez/jolt-chez.janet

@@ -20,7 +20,7 @@
   (each f ["host/chez/emit.janet" "host/chez/driver.janet" "host/chez/rt.ss"
            "host/chez/values.ss" "host/chez/collections.ss" "host/chez/seq.ss"
            "host/chez/atoms.ss" "host/chez/predicates.ss" "host/chez/regex.ss"
-           "host/chez/ns.ss" "host/chez/post-prelude.ss"]
+           "host/chez/ns.ss" "host/chez/post-prelude.ss" "host/chez/natives-meta.ss"]
     (array/push parts (slurp f)))
   (string/slice (string (hash (string/join parts))) 0))