Host shims and protocol fixes shaken out by aws-api

Running cognitect aws-api's pure test namespaces (signing/shapes/protocols/
util/retry/endpoints) surfaced general gaps:

- extend-protocol/extend-type accept a computed class type, e.g.
  (Class/forName "[B") for the byte-array class — the byte-array idiom data.json
  and aws-api use. The macro grouping handled only symbol/nil heads (it crashed on
  a list type); type->name resolves a Class value via .getName; a byte-array
  dispatches on the "[B" host tag.
- java.nio.ByteBuffer over a jolt byte-array (wrap/allocate/get/put/array/
  remaining/position/limit/duplicate/flip), plus extend-protocol to it.
- java.util.Arrays (equals/copyOf/copyOfRange/fill) and java.util.Random
  (nextBytes/nextInt/…).
- java.net.URI/create and clojure.lang.RT/baseLoader statics.
- clojure.core.async/promise-chan (deliver-once, peek-don't-pop).
- a failed java.time parse throws DateTimeParseException (typed), so
  (catch DateTimeParseException …) matches it instead of leaking an untyped
  condition.

The XML side lives in the jolt-lang/xml library (libxml2 over jolt.ffi); ByteBuffer
stays in core as a generic java.nio primitive.

Gate: make test green (corpus +6 JVM-certified rows, 0 NEW divergence; unit
553/553; SCI 211).

host/chez/io.ss

@@ -457,6 +457,10 @@
                   (if (jolt-nil? u) jolt-nil (host-new "StringReader" (jolt-slurp (url-strip-scheme (url-spec u))))))))))
 (register-class-statics! "ClassLoader" (list (cons "getSystemClassLoader" (lambda () the-classloader))))
 (register-class-statics! "java.lang.ClassLoader" (list (cons "getSystemClassLoader" (lambda () the-classloader))))
+;; clojure.lang.RT/baseLoader — the resource-resolving class loader (RT/baseLoader
+;; is how libraries reach Clojure's base loader, e.g. aws-api's resources ns).
+(register-class-statics! "RT" (list (cons "baseLoader" (lambda () the-classloader))))
+(register-class-statics! "clojure.lang.RT" (list (cons "baseLoader" (lambda () the-classloader))))
 ;; Thread/currentThread -> a fresh thread jhost wrapping THIS thread's interrupt
 ;; flag (the box from current-interrupt-box, host-static.ss), so .interrupt from
 ;; any thread sets the target thread's flag and .isInterrupted reads it without
@@ -583,6 +587,9 @@
 (define (uri-field u k) (let ((p (assq k (jhost-state u)))) (if p (cdr p) jolt-nil)))
 (register-class-ctor! "URI" (lambda (s) (uri-parse (jolt-str-render-one s))))
 (register-class-ctor! "java.net.URI" (lambda (s) (uri-parse (jolt-str-render-one s))))
+;; URI/create — the static factory, same as the (URI. s) constructor.
+(register-class-statics! "URI" (list (cons "create" (lambda (s) (uri-parse (jolt-str-render-one s))))))
+(register-class-statics! "java.net.URI" (list (cons "create" (lambda (s) (uri-parse (jolt-str-render-one s))))))
 (register-host-methods! "uri"
   (list (cons "toString" (lambda (u) (uri-field u 'string)))
         (cons "toASCIIString" (lambda (u) (uri-field u 'string)))