test+docs: spec coverage for migratus-enablement fixes; list migratus

Adds spec/conformance coverage for everything landed enabling migratus:
- conformance corpus (runs interpret/compile/self-host): def 3-arg docstring,
  def/defn ^{:map} name meta, defmacro arity-clause + docstring, defmulti
  docstring, assoc-nil/assoc-in real maps, try multi-body + finally-on-success,
  current-ns restore after a caught throw, cross-ns methods visibility.
- spec suites: host-interop (exception ctors, Character/Thread/Long, Timestamp/
  SimpleDateFormat, java.io.File model + File-aware file-seq, clojure.tools.logging),
  regex (Pattern statics + MULTILINE + quote, String .matches/.replaceAll/
  .replaceFirst), maps (assoc on nil), multimethods (defmulti docstring +
  value-based methods/get-method), macros (defmacro arity-clause + name meta).

Rewrote clojure.tools.logging/spy as a single variadic arity (jolt defmacro
takes only the first clause of a multi-arity macro — jolt-q8l).

docs/libraries.md: add migratus and the next.jdbc compatibility layer, with the
janet-lang/sqlite3 int64 caveat for 14-digit timestamp ids.

Full gate green; conformance 350/350 x3 modes.

test/spec/macros-spec.janet

@@ -85,3 +85,11 @@
   ["with-redefs-fn"      "42"     "(do (defn wr-i [] 1) (with-redefs-fn {(var wr-i) (fn [] 42)} (fn [] (wr-i))))"]
   ["macroexpand full"    "true"   "(let [e (macroexpand (quote (when-not false 1)))] (= (quote if) (first e)))"]
   ["macroexpand non-macro" "[1 2]" "(macroexpand (quote [1 2]))"])
+
+# defmacro accepts the arity-clause form (defmacro name ([params] body...)), a
+# leading docstring, and ^{:map} metadata on the name (jolt-whp, jolt-8w2).
+(defspec "macros / defmacro arity-clause & name metadata"
+  ["arity-clause form"    "10"  "(do (defmacro tw ([x] (list (quote *) x 2))) (tw 5))"]
+  ["docstring + arity"    "15"  "(do (defmacro th \"triple\" ([x] (list (quote *) x 3))) (th 5))"]
+  ["^{:map} name meta"    "7"   "(do (defmacro ^{:private true} pm [] 7) (pm))"]
+  ["multi-form body"      "6"   "(do (defmacro mb ([a b] (list (quote +) a b))) (mb 2 4))"])