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/unit/types-test.janet

@@ -0,0 +1,118 @@
+(use ../../src/jolt/types)
+
+# ============================================================
+# Var tests
+# ============================================================
+
+# make-var
+(let [v (make-var 'x 42)]
+  (assert (var? v) "var? returns true")
+  (assert (= 42 (var-get v)) "var-get returns root binding")
+  (assert (deep= {:name 'x} (var-meta v)) "var-meta returns metadata")
+  (assert (deep= 'x (var-name v)) "var-name returns name symbol"))
+
+# var without init value
+(let [v (make-var 'y)]
+  (assert (var? v) "unbound var is still a var"))
+
+# dynamic var
+(let [v (make-var '*dyn* 1 {:dynamic true})]
+  (assert (var-dynamic? v) "var-dynamic? true")
+  (assert (not (var-macro? v)) "var-macro? false for dynamic var"))
+
+# macro var
+(let [v (make-var 'when  nil {:macro true})]
+  (assert (var-macro? v) "var-macro? true"))
+
+# var-set — set root binding
+(let [v (make-var 'x 1)]
+  (var-set v 99)
+  (assert (= 99 (var-get v)) "var-set changes root binding"))
+
+# alter-var-root
+(let [v (make-var 'c 0)]
+  (alter-var-root v inc)
+  (assert (= 1 (var-get v)) "alter-var-root applies fn"))
+
+# with-meta — returns new var with updated meta
+(let [v (make-var 'x 42)
+      v2 (with-meta v {:private true})]
+  (assert (deep= {:name 'x :private true} (var-meta v2)) "with-meta merges meta")
+  (assert (= 42 (var-get v2)) "with-meta preserves root binding"))
+
+# var with namespace
+(let [ns (make-ns 'my.ns)
+      v (make-var 'my.ns/x 1 {:ns ns})]
+  (assert (= ns (var-ns v)) "var-ns returns namespace"))
+
+# ============================================================
+# Namespace tests
+# ============================================================
+
+(let [ns (make-ns 'foo.bar)]
+  (assert (ns? ns) "ns? returns true")
+  (assert (deep= 'foo.bar (ns-name ns)) "ns-name returns name symbol")
+  (assert (table? (ns-map ns)) "ns-map returns table")
+  (assert (= 0 (length (ns-map ns))) "empty namespace has no mappings"))
+
+# ns-intern
+(let [ns (make-ns 'test.ns)
+      v (ns-intern ns 'x 42)]
+  (assert (var? v) "ns-intern returns a var")
+  (assert (= 42 (var-get v)) "ns-intern sets root binding")
+  # check ns-find returns the same var (by reference, not deep=)
+  (assert (= v (ns-find ns 'x)) "ns-find returns interned var"))
+
+# ns-intern without value
+(let [ns (make-ns 'test.ns)
+      v (ns-intern ns 'y)]
+  (assert (var? v) "ns-intern without value creates unbound var"))
+
+# ns-unmap
+(let [ns (make-ns 'test.ns)
+      _ (ns-intern ns 'x 1)
+      _ (ns-unmap ns 'x)]
+  (assert (nil? (ns-find ns 'x)) "ns-unmap removes mapping"))
+
+# ns-resolve — own ns
+(let [ns (make-ns 'test.ns)
+      v (ns-intern ns 'x 10)]
+  (assert (= v (ns-resolve ns 'x)) "ns-resolve finds var in own ns"))
+
+# ns-import
+(let [ns (make-ns 'test.ns)]
+  (ns-import ns 'Date 'java.util.Date)
+  (assert (= 'java.util.Date (ns-import-lookup ns 'Date)) "ns-import-lookup returns import"))
+
+# ============================================================
+# Context tests
+# ============================================================
+
+(let [ctx (make-ctx)]
+  (assert (ctx? ctx) "ctx? returns true"))
+
+# ctx with initial namespaces
+(let [ctx (make-ctx {:namespaces {"user" {"x" 1 "y" 2}}})]
+  (let [ns (ctx-find-ns ctx "user")]
+    (assert (ns? ns) "ctx-find-ns returns namespace for user")
+    (let [v (ns-find ns "x")]
+      (assert (var? v) "user/x is a var")
+      (assert (= 1 (var-get v)) "user/x has correct value"))))
+
+# ctx-find-ns creates ns if not present
+(let [ctx (make-ctx)
+      ns (ctx-find-ns ctx "foo")]
+  (assert (ns? ns) "ctx-find-ns creates namespace on demand"))
+
+# ============================================================
+# Dynamic binding support (thread-local bindings table)
+# ============================================================
+
+# push-thread-bindings / pop-thread-bindings
+(let [v (make-var '*dyn* 0 {:dynamic true})]
+  (push-thread-bindings @{v 100})
+  (assert (= 100 (var-get v)) "push-thread-bindings sets binding")
+  (pop-thread-bindings)
+  (assert (= 0 (var-get v)) "pop-thread-bindings restores root"))
+
+(print "All types tests passed!")