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/eval.sx

@@ -5,20 +5,8 @@
 ;; ($if, $define!, $lambda, …) arrive in Phase 4, so tests build a
 ;; minimal env on the fly and verify the dispatch contract directly.
 
-(define ke-test-pass 0)
-(define ke-test-fail 0)
-(define ke-test-fails (list))
-
-(define
-  ke-test
-  (fn
-    (name actual expected)
-    (if
-      (= actual expected)
-      (set! ke-test-pass (+ ke-test-pass 1))
-      (begin
-        (set! ke-test-fail (+ ke-test-fail 1))
-        (append! ke-test-fails {:name name :actual actual :expected expected})))))
+(define ke-suite (refl-make-test-suite))
+(define ke-test  (fn (n a e) (refl-test ke-suite n a e)))
 
 ;; ── helpers ──────────────────────────────────────────────────────
 
@@ -267,4 +255,4 @@
       (kernel-eval (kernel-parse "(x 1)") env)))
   :raised)
 
-(define ke-tests-run! (fn () {:total (+ ke-test-pass ke-test-fail) :passed ke-test-pass :failed ke-test-fail :fails ke-test-fails}))
+(define ke-tests-run! (fn () (refl-test-report ke-suite)))