HS tests: add eval-hs helper, fix no/mathOperator/evalStatically suites

- eval-hs: new test helper that compiles+evaluates a HS expression and
  returns its result. Uses hs-to-sx-from-source with "return " prefix.
- Generator now emits eval-hs calls for expression-only tests
- no suite: 4/5 pass (was 0/5)
- evalStatically: 5/8 pass (was 0/8 stubs)
- pick: 7/7 pass (was 0/7 stubs)
- mathOperator: 3/5 pass (type issues on array concat)

477/831 (57.4%), +69 from session baseline of 408.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

spec/tests/test-hyperscript-behavioral.sx

@@ -16,6 +16,15 @@
   (fn ()
     (dom-set-inner-html (dom-body) "")))
 
+;; Evaluate a hyperscript expression and return its result.
+;; Compiles the expression, wraps in a thunk, evaluates, returns result.
+(define eval-hs
+  (fn (src)
+    (let ((sx (hs-to-sx-from-source (str "return " src))))
+      (let ((handler (eval-expr-cek
+              (list (quote fn) (list (quote me)) (list (quote let) (list (list (quote it) nil) (list (quote event) nil)) sx)))))
+        (handler nil)))))
+
 ;; ── add (19 tests) ──
 (defsuite "hs-upstream-add"
   (deftest "can add class ref on a single div"