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/metacircular.sx

@@ -12,20 +12,8 @@
 ;; first-class evaluators all line up — enough so a Kernel program
 ;; can itself reason about Kernel programs.
 
-(define kmc-test-pass 0)
-(define kmc-test-fail 0)
-(define kmc-test-fails (list))
-
-(define
-  kmc-test
-  (fn
-    (name actual expected)
-    (if
-      (= actual expected)
-      (set! kmc-test-pass (+ kmc-test-pass 1))
-      (begin
-        (set! kmc-test-fail (+ kmc-test-fail 1))
-        (append! kmc-test-fails {:name name :actual actual :expected expected})))))
+(define kmc-suite (refl-make-test-suite))
+(define kmc-test  (fn (n a e) (refl-test kmc-suite n a e)))
 
 ;; Build a Kernel env with m-eval and m-apply defined. The two refer
 ;; to each other and to standard primitives, so we use the standard
@@ -159,4 +147,4 @@
       env))
   49)
 
-(define kmc-tests-run! (fn () {:total (+ kmc-test-pass kmc-test-fail) :passed kmc-test-pass :failed kmc-test-fail :fails kmc-test-fails}))
+(define kmc-tests-run! (fn () (refl-test-report kmc-suite)))