HS: hoist emit-on throttle/debounce helpers to module level (perf)

Previous version put (define _throttle-ms ...) (define _debounce-ms ...)
(define _strip-throttle-debounce ...) inside emit-on's body, redefining
them on every call to emit-on. The kernel JIT-compiled the helper fn
fresh each invocation, doubling compile time across the suite and
pushing many tests over their wall-clock deadline (35 cumulative-only
timeouts in the latest batched run, up from 0).

Move the three definitions to module-level. Use (set! _throttle-ms nil)
(set! _debounce-ms nil) at the top of emit-on to reset state for each
call. JIT compilation of _strip-throttle-debounce now happens once.

Verified: hs-upstream-expressions/dom-scope went from 18/20 (with two
state-related timeouts) back to 20/20, suite wall-time 232s → 75s.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/hyperscript/compiler.sx

@@ -210,6 +210,28 @@
                             value)
                           (list (quote set!) (hs-to-sx target) value)))))))
               (true (list (quote set!) (hs-to-sx target) value)))))))
+    ;; Throttle/debounce extraction state — module-level so they don't get
+    ;; redefined on every emit-on call (which was causing JIT churn). Set
+    ;; via _strip-throttle-debounce at the start of each emit-on, used in
+    ;; the handler-build step inside scan-on.
+    (define _throttle-ms nil)
+    (define _debounce-ms nil)
+    (define
+      _strip-throttle-debounce
+      (fn
+        (lst)
+        (cond
+          ((<= (len lst) 1) lst)
+          ((= (first lst) :throttle)
+            (do
+              (set! _throttle-ms (nth lst 1))
+              (_strip-throttle-debounce (rest (rest lst)))))
+          ((= (first lst) :debounce)
+            (do
+              (set! _debounce-ms (nth lst 1))
+              (_strip-throttle-debounce (rest (rest lst)))))
+          (true
+            (cons (first lst) (_strip-throttle-debounce (rest lst)))))))
     (define
       emit-on
       (fn
@@ -218,27 +240,8 @@
           ((parts (rest ast)))
           (let
             ((event-name (first parts)))
-            ;; Pre-extract :throttle and :debounce kwargs (handler-wrapping modifiers)
-            ;; from parts so scan-on doesn't need extra params. Stored as closure vars
-            ;; that the handler-build step inside scan-on can read.
-            (define _throttle-ms nil)
-            (define _debounce-ms nil)
-            (define
-              _strip-throttle-debounce
-              (fn
-                (lst)
-                (cond
-                  ((<= (len lst) 1) lst)
-                  ((= (first lst) :throttle)
-                    (do
-                      (set! _throttle-ms (nth lst 1))
-                      (_strip-throttle-debounce (rest (rest lst)))))
-                  ((= (first lst) :debounce)
-                    (do
-                      (set! _debounce-ms (nth lst 1))
-                      (_strip-throttle-debounce (rest (rest lst)))))
-                  (true
-                    (cons (first lst) (_strip-throttle-debounce (rest lst)))))))
+            (set! _throttle-ms nil)
+            (set! _debounce-ms nil)
             (define
               scan-on
               (fn