sx-http: fix serialize_value for client-side parsing + remove debug code

serialize_value: lists with symbol head emit (fn args...) not (list fn args).
This lets the client SX parser recognise special forms like let, when, cond
inside component-defs. Data lists (starting with non-symbols) keep the
(list ...) wrapper.

Fixes "Undefined symbol: let" WASM error that broke all island hydration.
Header island now reaches the JIT evaluator (fails on for-each VM error,
not parsing). Geography, SXTP, CEK pages fully rendered.

Removed debug logging (ssr-debug, debug dump, debug endpoint).

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

hosts/ocaml/bin/sx_server.ml

@@ -53,7 +53,14 @@ let rec serialize_value = function
   | Symbol s -> s
   | Keyword k -> ":" ^ k
   | List items | ListRef { contents = items } ->
-    "(list " ^ String.concat " " (List.map serialize_value items) ^ ")"
+    (* Lists with a symbol head are call expressions: (fn arg1 arg2).
+       Lists starting with data values are data: (list 1 2 3).
+       This distinction matters for the client parser. *)
+    (match items with
+     | (Symbol _ | Keyword _) :: _ ->
+       "(" ^ String.concat " " (List.map serialize_value items) ^ ")"
+     | _ ->
+       "(list " ^ String.concat " " (List.map serialize_value items) ^ ")")
   | Dict d ->
     let pairs = Hashtbl.fold (fun k v acc ->
       (Printf.sprintf ":%s %s" k (serialize_value v)) :: acc) d [] in