Fix seven more JVM divergences (rewrite-clj full suite)

Running the whole rewrite-clj test suite (159 tests) surfaced seven more bugs;
with these it passes 3377/0/0. Each is a general jolt/JVM divergence:

- *out* was pinned to the startup stdout port, so (.write *out* …) escaped a
  with-out-str capture (z/print writes via *out*). It now resolves the live
  current-output-port, like print/__write, so a redirect is seen.
- nth / assoc past the end of a vector or seq threw a bare Chez error (class
  :object). Throw IndexOutOfBoundsException, matching the JVM.
- A number's .toString(radix) ignored the base. Render in the base, lowercase
  (rewrite-clj rebuilds 0xff / 0377 / 2r1001 through it).
- A required namespace's own :as aliases leaked into its requirer: the loaded ns
  form compiles while (chez-current-ns) is still the requirer, so ce-scan-requires!
  registered the loaded ns's aliases under the wrong ns and clobbered a same-named
  alias there. Register an (ns NAME …) form's aliases under NAME.
- A quoted collection dropped its metadata; now it keeps USER metadata (drops the
  reader's :line/:column/:file), like a Clojure quoted constant.
- enumeration-seq only did (seq e); it now drives a java.util.Enumeration through
  hasMoreElements/nextElement, and StringTokenizer implements them.

Regressions: corpus rows (with-out-str/*out*, nth/assoc bounds, toString radix,
quote metadata, enumeration-seq) certified against JVM; a smoke fixture for the
alias leak (a required ns's alias must not leak). tools.reader + rewrite-clj added
to docs/libraries.md. make test green.

host/chez/collections.ss

@@ -130,7 +130,7 @@
                     (vec-set (pvec-tail p) (fxand i pv-mask) x) #f)
            (mk-pvec cnt (pvec-shift p)
                     (pv-assoc-trie (pvec-shift p) (pvec-root p) i x) (pvec-tail p) #f)))
-      (else (error 'assoc "vector index out of bounds")))))
+      (else (jolt-throw (jolt-host-throwable "java.lang.IndexOutOfBoundsException" "vector index out of bounds"))))))
 (define (pvec-peek p)
   (let ((n (pvec-cnt p))) (if (fx=? n 0) jolt-nil (pvec-nth-d p (fx- n 1) jolt-nil))))
 ;; pop the last trie chunk back into the tail; #f means the subtree emptied.
@@ -449,9 +449,9 @@
      (let ((i (->idx i)))
        (cond ((pvec? coll) (let ((v (pvec-v coll)))
                              (if (and (fx>=? i 0) (fx<? i (vector-length v))) (vector-ref v i)
-                                 (error 'nth "index out of bounds"))))
+                                 (jolt-throw (jolt-host-throwable "java.lang.IndexOutOfBoundsException" "index out of bounds")))))
              ((string? coll) (if (and (fx>=? i 0) (fx<? i (string-length coll))) (string-ref coll i)
-                                 (error 'nth "index out of bounds")))
+                                 (jolt-throw (jolt-host-throwable "java.lang.IndexOutOfBoundsException" "index out of bounds"))))
              ((or (cseq? coll) (empty-list-t? coll)) (seq-nth coll i #f jolt-nil))
              ((rec-coll-method coll "nth") => (lambda (m) (jolt-invoke m coll i)))
              (else (error 'nth "unsupported collection")))))