test: restructure into unit / integration / spec layers + shared harness

Reorganize the flat 49-file test/ into three layers (jpm test recurses, so all
are still discovered):
- test/unit/        white-box component tests (reader, evaluator, types,
                    persistent-map, lazy-seq, macro, interop, compiler)
- test/integration/ cross-cutting + regression batteries (conformance, jank,
                    sci-bootstrap/runtime, features, systematic-coverage, api,
                    core, namespaces, ported clojure suites) and
   .../ports/       ported clojure/cljs test batches pending consolidation
- test/spec/        the behavioral contract (built out in following commits)
- test/support/harness.janet  shared defspec table runner (cases compared via
                    Jolt's own =, with a :throws sentinel) + expect= helpers

Files moved with git mv (history preserved) and import paths fixed for depth.
jpm test green. README Test section updated.

Next: build out test/spec/ to cover the public API area-by-area, mining the
integration batteries and filling gaps.

test/integration/clojure-macros-test.janet

@@ -0,0 +1,63 @@
+# Ported from clojure/test_clojure/macros.clj
+(use ../../src/jolt/api)
+(defn ct-eval [ctx s] (normalize-pvecs (eval-string ctx s)))
+
+(print "Ported Macros Tests")
+
+# --- -> and ->> threading ---
+(print "test -> and ->>...")
+(let [ctx (init)]
+  (ct-eval ctx "(defmacro c [arg] (if (= 'b (first arg)) :foo :bar))")
+  (ct-eval ctx "(def a 2)")
+  (ct-eval ctx "(def b identity)")
+  (assert (= :foo (ct-eval ctx "(-> a b c)")) "-> threading")
+  (assert (= :foo (ct-eval ctx "(->> a b c)")) "->> threading"))
+(print "  ok")
+
+# --- some-> ---
+(print "test some->...")
+(let [ctx (init)]
+  (assert (= nil (ct-eval ctx "(some-> nil)")) "some-> nil")
+  (assert (= 0 (ct-eval ctx "(some-> 0)")) "some-> 0")
+  (assert (= -1 (ct-eval ctx "(some-> 1 (- 2))")) "some-> with form")
+  (ct-eval ctx "(defn const-nil [_] nil)")
+  (assert (= nil (ct-eval ctx "(some-> 1 const-nil (- 2))")) "some-> stop at nil"))
+(print "  ok")
+
+# --- some->> ---
+(print "test some->>...")
+(let [ctx (init)]
+  (assert (= nil (ct-eval ctx "(some->> nil)")) "some->> nil")
+  (assert (= 0 (ct-eval ctx "(some->> 0)")) "some->> 0")
+  (assert (= 1 (ct-eval ctx "(some->> 1 (- 2))")) "some->> with form")
+  (ct-eval ctx "(defn const-nil2 [_] nil)")
+  (assert (= nil (ct-eval ctx "(some->> 1 const-nil2 (- 2))")) "some->> stop at nil"))
+(print "  ok")
+
+# --- cond-> ---
+(print "test cond->...")
+(let [ctx (init)]
+  (assert (= 0 (ct-eval ctx "(cond-> 0)")) "cond-> single")
+  (assert (= -1 (ct-eval ctx "(cond-> 0 true inc true (- 2))")) "cond-> with tests")
+  (assert (= 0 (ct-eval ctx "(cond-> 0 false inc)")) "cond-> false test")
+  (assert (= -1 (ct-eval ctx "(cond-> 1 true (- 2) false inc)")) "cond-> mix"))
+(print "  ok")
+
+# --- cond->> ---
+(print "test cond->>...")
+(let [ctx (init)]
+  (assert (= 0 (ct-eval ctx "(cond->> 0)")) "cond->> single")
+  (assert (= 1 (ct-eval ctx "(cond->> 0 true inc true (- 2))")) "cond->> with tests")
+  (assert (= 0 (ct-eval ctx "(cond->> 0 false inc)")) "cond->> false test")
+  (assert (= 1 (ct-eval ctx "(cond->> 1 true (- 2) false inc)")) "cond->> mix"))
+(print "  ok")
+
+# --- as-> ---
+(print "test as->...")
+(let [ctx (init)]
+  (assert (= 0 (ct-eval ctx "(as-> 0 x)")) "as-> single")
+  (assert (= 1 (ct-eval ctx "(as-> 0 x (inc x))")) "as-> one form")
+  (assert (= 2 (ct-eval ctx "(as-> [0 1] x (map inc x) (reverse x) (first x))")) "as-> chain"))
+(print "  ok")
+
+(print "\nAll Ported Macros tests passed!")