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/smoke.sh

@@ -93,6 +93,17 @@ else
   fails=$((fails + 1))
 fi
 
+# A required namespace's own :as aliases must not leak into the requirer: fix.main
+# aliases clojure.string as ss and requires fix.lib (which aliases clojure.set as
+# ss); (ss/upper-case "hi") in main must stay clojure.string -> "HI #{1 2}".
+al_out="$(JOLT_PWD="$root/test/chez/alias-leak-app" bin/joltc run -m fix.main 2>/dev/null | tail -1)"
+if [ "$al_out" = "HI #{1 2}" ]; then
+  pass=$((pass + 1))
+else
+  echo "  FAIL: a loaded ns's alias leaked into its requirer — got \`$al_out\`, want \`HI #{1 2}\`"
+  fails=$((fails + 1))
+fi
+
 # Unit-checks the REPL read-until-complete predicate over balanced/unbalanced,
 # string, comment and regex-literal inputs. A multi-form `joltc run` so jolt.main
 # is loaded and its private var resolves; the file self-checks and prints a sentinel.