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/jank-conformance.janet

@@ -1,54 +0,0 @@
-# jank conformance: runs the Clojure-language pass-tests from a local jank
-# checkout (https://github.com/jank-lang/jank, MPL-2.0) against Jolt and asserts
-# the number that pass stays at/above a baseline. This does NOT vendor jank's
-# sources (license differs) — it references ~/src/jank if present and SKIPS
-# cleanly when absent, so it is a local/dev regression aid.
-#
-# Each jank pass-test is an assertion script ending in `:success`. We load it in
-# a fresh context and count it as passing when it returns :success.
-(use ../src/jolt/api)
-
-(def jank-dir (string (os/getenv "HOME") "/src/jank/compiler+runtime/test/jank"))
-
-# Baseline: the number of pass-tests Jolt currently handles. Raise this as Jolt
-# gains features so regressions (a previously-passing test breaking) are caught.
-(def baseline 120)
-
-# Tests that loop forever under Jolt's eager evaluation (skipped to avoid hangs;
-# tracked as known gaps — variadic-recur arity selection and var-quote calls).
-(def skip-patterns ["/cpp/" "var-quote" "fn/recur/pass-variadic-position"])
-
-(defn- skip? [path]
-  (var s false)
-  (each p skip-patterns (when (string/find p path) (set s true)))
-  s)
-
-(defn- walk [dir acc]
-  (each e (os/dir dir)
-    (def p (string dir "/" e))
-    (case ((os/stat p) :mode)
-      :directory (walk p acc)
-      :file (when (and (string/has-suffix? ".jank" p)
-                       (string/find "/pass-" p)
-                       (not (skip? p)))
-              (array/push acc p))))
-  acc)
-
-(if (not (os/stat jank-dir))
-  (print "jank-conformance: ~/src/jank not present — skipped")
-  (do
-    (def files (sort (walk jank-dir @[])))
-    (var pass 0)
-    (def fails @[])
-    (each f files
-      # A pass-test passes when no assertion throws (assert now errors on failure).
-      (def res (protect (load-string (init) (slurp f))))
-      (if (= (res 0) true)
-        (++ pass)
-        (array/push fails (string/slice f (+ 1 (length jank-dir))))))
-    (printf "jank-conformance: %d/%d pass-tests pass (baseline %d)" pass (length files) baseline)
-    (when (< pass baseline)
-      (print "--- regressions (now failing, were within baseline) ---")
-      (each rel fails (print "  " rel))
-      (error (string "jank conformance dropped to " pass " (baseline " baseline ")")))
-    (printf "jank conformance OK (%d known gaps)" (length fails))))