haskell: typecheck.sx 10/15→15/15 + plan Phases 20-22 (HM gaps, classes, integration)

Five "typed ok: …" tests in tests/typecheck.sx compared an unforced thunk
against an integer/list. The untyped-path convention is hk-deep-force on
the result; hk-run-typed follows the same shape but the tests omitted
that wrap. Added hk-deep-force around hk-run-typed in those five tests.
typecheck.sx now 15/15; infer.sx still 75/75.

Plan adds three phases capturing the remaining type-system work:
- Phase 20: Algorithm W gaps (case, do, record accessors, expression
  annotations).
- Phase 21: type classes with qualified types ([Eq a] => …) and
  constraint propagation, integrated with the existing dict-passing
  evaluator.
- Phase 22: typecheck-then-run as the default conformance path, with a
  ≥ 30/36 typechecking threshold before swap.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/haskell/tests/typecheck.sx

@@ -16,15 +16,18 @@
       true)))
 
 ;; ─── Valid programs pass through ─────────────────────────────────────────────
-(hk-test "typed ok: simple arithmetic" (hk-run-typed "main = 1 + 2") 3)
+(hk-test "typed ok: simple arithmetic"
+  (hk-deep-force (hk-run-typed "main = 1 + 2")) 3)
 
-(hk-test "typed ok: boolean" (hk-run-typed "main = True") (list "True"))
+(hk-test "typed ok: boolean"
+  (hk-deep-force (hk-run-typed "main = True")) (list "True"))
 
-(hk-test "typed ok: let binding" (hk-run-typed "main = let x = 1 in x + 2") 3)
+(hk-test "typed ok: let binding"
+  (hk-deep-force (hk-run-typed "main = let x = 1 in x + 2")) 3)
 
 (hk-test
   "typed ok: two independent fns"
-  (hk-run-typed "f x = x + 1\nmain = f 5")
+  (hk-deep-force (hk-run-typed "f x = x + 1\nmain = f 5"))
   6)
 
 ;; ─── Untypeable programs are rejected ────────────────────────────────────────
@@ -76,7 +79,7 @@
 
 (hk-test
   "run-typed sig ok: Int declared matches"
-  (hk-run-typed "main :: Int\nmain = 1 + 2")
+  (hk-deep-force (hk-run-typed "main :: Int\nmain = 1 + 2"))
   3)
 
 {:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}