Replace str-render/instance-check set! chains with registries

jolt-str-render-one and instance-check were each extended by a chain of
set!-wrapping closures spread across ~10 and ~5 host files, so the real
behavior of either was scattered and load-order-dependent. Give each a
registry the base file owns: converters.ss/records-interop.ss define the
registry plus a register-* helper, and each extending file registers one arm
instead of capturing %prev and set!-ing the global.

str-render arms are type-disjoint; instance-check arms run newest-first (the
old outermost-wins order) and may return 'pass to defer. The string-token ->
symbol normalization the natives-array arm did for every inner arm moves to
the dispatcher head; array tokens stay strings for that arm to decide.

jolt-ogib.14. Runtime-only shims, no re-mint.

host/chez/records.ss

@@ -410,14 +410,11 @@
 ;; jolt exception values (ex-info + host-constructed throwables) are ex-info-shaped
 ;; maps tagged :jolt/type :jolt/ex-info; (class …)/instance? read the JVM class off
 ;; the optional :jolt/class key, defaulting to clojure.lang.ExceptionInfo.
-(define %r-str-render-one jolt-str-render-one)
-(set! jolt-str-render-one
+(register-str-render! jrec?
   (lambda (v)
-    (if (jrec? v)
-        (let ((f (find-protocol-method (jrec-tag v) "Object" "toString")))
-          (if f (jolt-invoke f v)
-              (let ((s (jrec-pr v))) (substring s 1 (string-length s)))))
-        (%r-str-render-one v))))
+    (let ((f (find-protocol-method (jrec-tag v) "Object" "toString")))
+      (if f (jolt-invoke f v)
+          (let ((s (jrec-pr v))) (substring s 1 (string-length s)))))))
 
 ;; `type` lives in natives-meta.ss: it needs jolt-meta for the :type
 ;; override and a total value->taxonomy mapping, so it sits with meta — a record