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/encap.sx

@@ -5,20 +5,8 @@
 ;; identity is per-call, so two `(make-encapsulation-type)` calls
 ;; produce non-interchangeable families.
 
-(define ken-test-pass 0)
-(define ken-test-fail 0)
-(define ken-test-fails (list))
-
-(define
-  ken-test
-  (fn
-    (name actual expected)
-    (if
-      (= actual expected)
-      (set! ken-test-pass (+ ken-test-pass 1))
-      (begin
-        (set! ken-test-fail (+ ken-test-fail 1))
-        (append! ken-test-fails {:name name :actual actual :expected expected})))))
+(define ken-suite (refl-make-test-suite))
+(define ken-test  (fn (n a e) (refl-test ken-suite n a e)))
 
 (define ken-eval-in (fn (src env) (kernel-eval (kernel-parse src) env)))
 
@@ -180,4 +168,4 @@
       env))
   (list true 7))
 
-(define ken-tests-run! (fn () {:total (+ ken-test-pass ken-test-fail) :passed ken-test-pass :failed ken-test-fail :fails ken-test-fails}))
+(define ken-tests-run! (fn () (refl-test-report ken-suite)))