Class/forName honesty + class/isa? conformance for builtins

Class/forName claimed every java.*/clojure.* name found (and any "x.y.Class"
matched the registered Class via a short-name fallback), so a library's
(class-found? "optional.Dep") feature-probe always said yes — tools.logging then
tried to build the java.util.logging / log4j backends jolt lacks and crashed.
Resolve forName by exact registry lookup + an honest prefix that excludes the
unbacked optional packages (java.util.logging, javax.management), so the probe
sees them absent and skips the backend.

class of a persistent collection / namespace now reports its JVM class name
(clojure.lang.PersistentHashSet, …Namespace, …) instead of jolt's internal :set/
:object tag, and isa? consults JVM class assignability — Object as every class's
root plus a modeled clojure.lang/java.util hierarchy — so (isa? (class x) C) and a
class-keyed multimethod dispatch like the JVM (e.g. (isa? Keyword Object) was
false). Adds the bare class tokens (Fn/Namespace/Set/…) these dispatch on.

(type x) is unchanged — it keeps jolt's documented internal-keyword form. Six
JVM-certified corpus rows. make test green, 0 new divergences.

jolt-core/clojure/core/20-coll.clj

@@ -302,6 +302,9 @@
   ([child parent] (isa? (deref global-hierarchy) child parent))
   ([h child parent]
    (or (= child parent)
+       ;; JVM class assignability (Object root + modeled clojure.lang/java.* ancestry),
+       ;; so a class-keyed multimethod / (isa? (class x) C) dispatches like the JVM.
+       (jolt.host/class-isa? child parent)
        (contains? (get (get h :ancestors) child #{}) parent)
        (and (vector? parent) (vector? child)
             (= (count parent) (count child))