Library ports: get hiccup running, verify malli (reader + interop fixes) (#127)

* Reader: #() params survive syntax-quote (auto-gensym names)

#(...) named its synthesized params with bare gensyms, so a #() written inside a
syntax-quote had its params qualified to the current ns by sq-symbol — and a
qualified symbol isn't a valid fn param. hiccup's compiler emits
`(let [sb# ..] (iterate! #(.append sb# %) ..)), which broke with "Unable to
resolve symbol: ns/_NNNN".

Name the params with a trailing # (auto-gensym suffix, like Clojure's p1__N#) so
syntax-quote maps them consistently and leaves them unqualified. Harmless outside
a backtick (just a regular symbol name).

* interop: String/valueOf static + String is a CharSequence

Two interop gaps surfaced bringing up hiccup and malli:
- String/valueOf(Object): hiccup's compiler stringifies attribute values with
  (String/valueOf (or arg "")). Added the static — "null" for nil, else core-str.
- (instance? CharSequence s) returned false for a string; String implements
  CharSequence, and malli's :re validator gates on it before matching, so :re
  schemas always failed. instance-check now answers true for strings.

---------

Co-authored-by: Yogthos <yogthos@gmail.com>

src/jolt/interop/host_io.janet

@@ -288,6 +288,12 @@
   # (String. bytes) / (String. bytes charset): UTF-8 bytes to string.
   (each nm ["String" "java.lang.String"]
     (register-class-ctor! nm (fn [x &opt charset] (string x))))
+  # String statics. valueOf(Object) yields "null" for nil, else toString —
+  # hiccup's compiler emits (String/valueOf (or arg "")) to stringify attribute
+  # values; core-str gives jolt's str semantics for keywords/numbers/etc.
+  (each nm ["String" "java.lang.String"]
+    (register-class-statics! nm
+      @{"valueOf" (fn [x &opt off cnt] (if (nil? x) "null" (core-str x)))}))
   # java.net.URL: enough for selmer's template cache — file: URLs only.
   # A protocol-less spec throws (selmer catches MalformedURLException and
   # prepends file:///), and getPath hands back a stat-able filesystem path.