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/natives-meta.ss

@@ -12,6 +12,13 @@
 (define (jolt-meta x)
   (cond
     ((symbol-t? x) (let ((m (symbol-t-meta x))) (if (jolt-nil? m) jolt-nil m)))
+    ;; a var's meta is {:ns :name} (derived from the cell) + any def-time user
+    ;; meta from rt.ss's var-meta-table (jolt-zikh).
+    ((var-cell? x)
+     (let ((user (hashtable-ref var-meta-table x #f)))
+       (jolt-assoc (if user user (jolt-hash-map))
+                   jolt-kw-var-ns (var-cell-ns x)
+                   jolt-kw-var-name (var-cell-name x))))
     ((or (pvec? x) (pmap? x) (pset? x) (cseq? x) (empty-list-t? x) (jrec? x) (procedure? x))
      (hashtable-ref meta-table x jolt-nil))
     (else jolt-nil)))