feat: jolt-side java.sql interop + defn/defmacro meta & arity-clause fixes

For the migratus next.jdbc shim (jolt-0z5):
- core.janet: __jdbc-wrap-conn / __jdbc-conn-raw / __jdbc-make-stmt builtins.
  A connection is a tagged wrapper over a jdbc.core conn carrying a clj :exec
  callback so the host Statement.executeBatch runs SQL without a janet->clj call.
- javatime.janet: tagged-methods for :jolt/jdbc-conn (setAutoCommit/isClosed/
  close/getMetaData), :jolt/jdbc-meta (getDatabaseProductName), :jolt/jdbc-stmt
  (addBatch/executeBatch/close); java.sql.Timestamp ctor -> millis.
- evaluator.janet: instance? case for Connection/java.sql.Connection so
  migratus's do-commands runs SQL through its Connection branch.

Two defn/defmacro fixes found loading migratus.core (both rooted in the reader
representing ^{:map} name metadata as a with-meta form, jolt-8w2):
- defmacro special form: unwrap a with-meta name (mirrors def), and handle the
  arity-clause form (defmacro name ([params] body...)) like fn/defn — a params
  vector reads as a tuple, an arity clause as a list (array).
- defn overlay: pass the bare (unwrapped) name to fn while def keeps the meta.

Conformance 335/335 x3 modes.

jolt-core/clojure/core/00-syntax.clj

@@ -341,10 +341,14 @@
 (defmacro defn [fn-name & body]
   (let [body (if (and (seq body) (string? (first body))) (rest body) body)
         body (if (and (seq body) (map? (first body)) (not (symbol? (first body))))
-               (rest body) body)]
+               (rest body) body)
+        ;; ^{:map} metadata on the name reads as a (with-meta sym …) form, not an
+        ;; annotated symbol (jolt-8w2). def attaches the metadata, but fn needs a
+        ;; bare symbol, so unwrap it for the fn name.
+        fn-only-name (if (symbol? fn-name) fn-name (first (rest fn-name)))]
     ;; pass the name through to fn: the compiled fn's janet name carries it,
     ;; so stack traces read app.deep/level3 instead of a gensym (jolt-2o7.1)
-    `(def ~fn-name (fn ~fn-name ~@body))))
+    `(def ~fn-name (fn ~fn-only-name ~@body))))
 
 ;; Jolt doesn't enforce privacy, so defn- is just defn (matching how Clojure's own
 ;; defn- delegates to defn with :private metadata).