spec: gensym + symbol interning — *gensym-counter*, string->symbol, symbol->string, intern

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

spec/evaluator.sx

@@ -4754,3 +4754,25 @@
   (fn
     (val)
     (if (thunk? val) (eval-expr (thunk-expr val) (thunk-env val)) val)))
+
+;; Phase 12: gensym + symbol interning
+
+(define *gensym-counter* 0)
+
+(define
+  gensym
+  (fn
+    (&rest args)
+    (let
+      ((prefix (if (empty? args) "g" (str (first args)))))
+      (do
+        (set! *gensym-counter* (+ *gensym-counter* 1))
+        (make-symbol (str prefix *gensym-counter*))))))
+
+(define string->symbol (fn (s) (make-symbol s)))
+
+(define symbol->string (fn (sym) (symbol-name sym)))
+
+(define intern (fn (s) (make-symbol s)))
+
+(define symbol-interned? (fn (sym) true))