spec: gensym + symbol interning (OCaml + tests)

gensym_counter ref + gensym/string->symbol/symbol->string/intern/symbol-interned?
primitives in sx_primitives.ml. Fix ListRef case in seq_to_list on both
sx_ref.ml and sx_primitives.ml. 19 new tests in test-gensym.sx.
OCaml 4450/1080, JS 2205/2497, zero regressions.

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

hosts/ocaml/lib/sx_primitives.ml

@@ -99,6 +99,8 @@ let rec to_string = function
   | RawHTML s -> s
   | v -> inspect v
 
+let gensym_counter = ref 0
+
 let () =
   (* === Arithmetic === *)
   register "+" (fun args ->
@@ -2118,6 +2120,7 @@ let () =
     match v with
     | Nil -> List []
     | List _ -> v
+    | ListRef { contents = items } -> List items
     | Vector arr -> List (Array.to_list arr)
     | String s ->
       let chars = ref [] in
@@ -2197,4 +2200,29 @@ let () =
         if (step > 0 && i >= hi) || (step < 0 && i <= hi) then acc
         else build (i + step) (Integer i :: acc) in
       List (List.rev (build lo []))
-    | _ -> raise (Eval_error "in-range: expected (end) or (start end) or (start end step)"))
+    | _ -> raise (Eval_error "in-range: expected (end) or (start end) or (start end step)"));
+  (* === gensym + symbol interning === *)
+  register "gensym" (fun args ->
+    let prefix = match args with
+      | [] -> "g"
+      | [String s] -> s
+      | [Symbol s] -> s
+      | _ -> raise (Eval_error "gensym: expected optional prefix string") in
+    incr gensym_counter;
+    Symbol (prefix ^ string_of_int !gensym_counter));
+  register "string->symbol" (fun args ->
+    match args with
+    | [String s] -> Symbol s
+    | _ -> raise (Eval_error "string->symbol: expected 1 string"));
+  register "symbol->string" (fun args ->
+    match args with
+    | [Symbol s] -> String s
+    | _ -> raise (Eval_error "symbol->string: expected 1 symbol"));
+  register "intern" (fun args ->
+    match args with
+    | [String s] -> Symbol s
+    | _ -> raise (Eval_error "intern: expected 1 string"));
+  register "symbol-interned?" (fun args ->
+    match args with
+    | [Symbol _] -> Bool true
+    | _ -> raise (Eval_error "symbol-interned?: expected 1 symbol"))

hosts/ocaml/lib/sx_ref.ml

@@ -29,6 +29,7 @@ let seq_to_list v =
   match v with
   | Nil -> List []
   | List _ -> v
+  | ListRef { contents = items } -> List items
   | Vector arr -> List (Array.to_list arr)
   | String s ->
     let chars = ref [] in