Fix JIT compile-let shadow binding: evaluate init before defining local

compile-let called scope-define-local eagerly as part of the let
binding, adding the new local to the scope before compile-expr ran
for the init expression. When nested lets rebound the same variable
(e.g. the hyperscript parser's 4 chained `parts` bindings), the init
expression resolved the name to the new uninitialized slot instead of
the outer one — producing nil where it should have read the previous
value.

Move scope-define-local after compile-expr so init expressions see the
outer scope's binding. Fixes all 11 JIT hyperscript parser failures.
3127/3127 JIT + non-JIT, 25/25 standalone hyperscript tests.

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

lib/hyperscript/test-closure.sx

@@ -0,0 +1,13 @@
+;; Minimal test: define-inside-let pattern (like hs-parse)
+(define
+  test-closure-parse
+  (fn
+    (tokens)
+    (let
+      ((p 0) (tok-len (len tokens)))
+      (define get-val (fn () (get (nth tokens p) "value")))
+      (define advance! (fn () (set! p (+ p 1))))
+      (let
+        ((first-val (get-val)))
+        (advance!)
+        (list "first:" first-val "second:" (get-val) "p:" p)))))