Compiler: letrec for skip-annotations in compile-define

Self-referencing local function used let instead of letrec, causing
JIT failures: "VM undefined: skip-annotations" when compiling any
define with type annotations (:effects, :as). Retranspile needed
to eliminate JIT fallback warnings from the OCaml binary.

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

lib/compiler.sx

@@ -728,7 +728,7 @@
                   (and
                     (not (empty? rest-args))
                     (= (type-of (first rest-args)) "keyword"))
-                  (let
+                  (letrec
                     ((skip-annotations (fn (items) (if (empty? items) nil (if (= (type-of (first items)) "keyword") (skip-annotations (rest (rest items))) (first items))))))
                     (skip-annotations rest-args))
                   (first rest-args)))))