test-runner: extract harness kit + migrate Kernel (7 files, 84 LoC saved)

lib/guest/test-runner.sx — per-suite mutable state {:pass :fail :fails}
+ refl-test recorder + refl-test-report. Replaces the identical
4-define harness that appears in 142+ test files across the codebase.

Each migrated file goes from:
  (define X-test-pass 0)
  (define X-test-fail 0)
  (define X-test-fails (list))
  (define X-test (fn (name actual expected) (if (= actual expected)
    (set! X-test-pass (+ X-test-pass 1)) (begin ...))))
  ;; ... tests ...
  (define X-tests-run! (fn () {:total ... :passed ... :failed ... :fails ...}))

to:
  (define X-suite (refl-make-test-suite))
  (define X-test  (fn (n a e) (refl-test X-suite n a e)))
  ;; ... tests ...
  (define X-tests-run! (fn () (refl-test-report X-suite)))

All 322 Kernel tests pass unchanged (parse 62, eval 36, vau 38,
standard 127, encap 19, hygiene 26, metacircular 14). 84 LoC removed.

Migration is mechanical (the prefix is the only difference between
suites); /tmp/migrate_harness.py drives the regex. Other guests
(Tcl, Smalltalk, APL, CL, Erlang, Haskell, etc.) migrated in
subsequent commits.

lib/kernel/tests/vau.sx

@@ -5,20 +5,8 @@
 ;; base-env, bind a few helper applicatives (+, *, list, =, $if), and
 ;; run programs that construct and use custom combiners.
 
-(define kv-test-pass 0)
-(define kv-test-fail 0)
-(define kv-test-fails (list))
-
-(define
-  kv-test
-  (fn
-    (name actual expected)
-    (if
-      (= actual expected)
-      (set! kv-test-pass (+ kv-test-pass 1))
-      (begin
-        (set! kv-test-fail (+ kv-test-fail 1))
-        (append! kv-test-fails {:name name :actual actual :expected expected})))))
+(define kv-suite (refl-make-test-suite))
+(define kv-test  (fn (n a e) (refl-test kv-suite n a e)))
 
 (define kv-eval-src (fn (src env) (kernel-eval (kernel-parse src) env)))
 
@@ -306,4 +294,4 @@
 (kv-test "lambda: zero-arg multi-body"
   (kv-eval-src "(($lambda () 1 2 3))" (kv-make-env)) 3)
 
-(define kv-tests-run! (fn () {:total (+ kv-test-pass kv-test-fail) :passed kv-test-pass :failed kv-test-fail :fails kv-test-fails}))
+(define kv-tests-run! (fn () (refl-test-report kv-suite)))