Chez Phase 2 (inc U): list? + map-entry-as-vector + clojure.walk (jolt-75sv)

list? was nil on Chez because one cseq record backs both lists and lazy/
realized seqs. Add a list? marker field (cseq v2) set only on the HEAD cell
of a list -- (list ...), quoted list literals, cons, reverse, conj onto a
list. rest/next/seq/map therefore yield unmarked seq cells, so they are
seqs and not list?, matching the seed (where rest-of-a-list is a non-list
seq). Empty () is treated as a list.

vector?: drop the map-entry exclusion. Clojure's MapEntry implements
IPersistentVector and the seed agrees -- (vector? (first {:a 1})) is true.
Only dot-forms' coll dispatch read jolt-vector?, where a 2-vector entry is
correct.

clojure.walk + clojure.template join the prelude stdlib tier. The driver
now evals each stdlib ns's requires -- and the ns form's (:require ...)
clause -- so an aliased ref (template's walk/postwalk-replace) resolves at
emit time instead of lowering to an Unknown class host-static. ns forms are
evaled for that side effect but not emitted, so the runtime *ns* doesn't
leak to the last stdlib ns.

Parity 2163 -> 2176, 0 new divergences. New test/chez/_walk.janet 39/39.

host/chez/predicates.ss

@@ -8,11 +8,15 @@
 ;; seed predicates are simply absent here for now.
 
 (define (jolt-map? x) (pmap? x))
-;; a map entry is a pvec under the hood but is NOT vector? (matches Clojure's
-;; MapEntry — jolt-agw6); the public vector? predicate excludes it.
-(define (jolt-vector? x) (and (pvec? x) (not (pvec-ent x))))
+;; a map entry is a pvec under the hood AND is vector? — Clojure's MapEntry
+;; implements IPersistentVector, so (vector? (first {:a 1})) is true (the seed
+;; agrees; jolt-75sv corrected the earlier exclusion).
+(define (jolt-vector? x) (pvec? x))
 (define (jolt-set? x) (pset? x))
 (define (jolt-seq? x) (or (cseq? x) (empty-list-t? x)))
+;; (list? x): a list-marked cseq node or the empty list (). A lazy/vector-backed
+;; seq, (rest list), (seq coll), (map …) are seqs but not lists (jolt-75sv).
+(define (jolt-list-pred? x) (or (and (cseq? x) (cseq-list? x)) (empty-list-t? x)))
 (define (jolt-coll-pred? x)
   (or (pvec? x) (pmap? x) (pset? x) (cseq? x) (empty-list-t? x)))
 (define (jolt-number? x) (number? x))
@@ -52,6 +56,7 @@
 (def-var! "clojure.core" "vector?" jolt-vector?)
 (def-var! "clojure.core" "set?" jolt-set?)
 (def-var! "clojure.core" "seq?" jolt-seq?)
+(def-var! "clojure.core" "list?" jolt-list-pred?)
 (def-var! "clojure.core" "coll?" jolt-coll-pred?)
 (def-var! "clojure.core" "fn?" jolt-fn?)
 (def-var! "clojure.core" "boolean?" jolt-boolean-pred?)