sx-http: SX adapter for all SSR — islands render correctly

Switch SSR + shell from native Sx_render to SX adapter (render-to-html
from adapter-html.sx) via CEK evaluator. Handles reactive primitives
(signals, deref, computed) for island bodies. Native renderer as fallback.

Header island SSRs correctly: (<sx>), tagline, copyright, path.
Stepper renders body but ~cssx/tw shows as raw SX (client-affinity
component not expanded server-side, client not expanding either).

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

hosts/ocaml/bin/sx_server.ml

@@ -1517,29 +1517,30 @@ let http_render_page env path =
       | String s | SxExpr s -> s
       | _ -> serialize_value body_result
     in
-    (* Debug: dump aser for homepage *)
-    if path = "/sx/" then begin
-      try
-        let oc = open_out "/tmp/sx-aser-home.txt" in
-        output_string oc body_str;
-        close_out oc;
-        Printf.eprintf "[debug] Wrote aser for %s: %d bytes\n%!" path (String.length body_str)
-      with _ -> ()
-    end;
     let t2 = Unix.gettimeofday () in
-    (* Phase 2: SSR — render to HTML using streaming buffer renderer.
+    (* Phase 2: SSR — render to HTML using the SX adapter (render-to-html
-       Writes directly to buffer, no intermediate string allocations. *)
+       from adapter-html.sx) via the CEK evaluator. This handles reactive
+       primitives (signals, deref, computed) correctly for island SSR.
+       Falls back to native Sx_render if the SX adapter isn't available. *)
     let body_html =
       try
         let body_exprs = Sx_parser.parse_all body_str in
         let body_expr = match body_exprs with
           | [e] -> e | [] -> Nil | _ -> List (Symbol "<>" :: body_exprs) in
-        let buf = Buffer.create 65536 in
+        if env_has env "render-to-html" then begin
-        (try Sx_render.render_to_buffer buf body_expr env
+          (* SX adapter — handles signals, islands, CSSX *)
-         with e -> Printf.eprintf "[http-ssr] partial for %s: %s\n%!" path (Printexc.to_string e));
+          let render_call = List [Symbol "render-to-html";
-        Buffer.contents buf
+                                  List [Symbol "quote"; body_expr];
+                                  Env env] in
+          let result = Sx_ref.eval_expr render_call (Env env) in
+          match result with
+          | String s | RawHTML s -> s
+          | _ -> Sx_runtime.value_to_str result
+        end else
+          (* Fallback: native renderer *)
+          Sx_render.render_to_html_streaming body_expr env
       with e ->
-        Printf.eprintf "[http-ssr] failed: %s\n%!" (Printexc.to_string e); ""
+        Printf.eprintf "[http-ssr] failed for %s: %s\n%!" path (Printexc.to_string e); ""
     in
     let t3 = Unix.gettimeofday () in
     (* Phase 3: Shell — render directly to buffer for zero-copy output *)
@@ -1567,7 +1568,19 @@ let http_render_page env path =
       Keyword "meta-html"; String "";
     ] in
     let shell_call = List (Symbol "~shared:shell/sx-page-shell" :: shell_args) in
-    let html = Sx_render.render_to_html_streaming shell_call env in
+    (* Use SX adapter for shell too — it's an SX component *)
+    let html =
+      if env_has env "render-to-html" then begin
+        let render_call = List [Symbol "render-to-html";
+                                List [Symbol "quote"; shell_call];
+                                Env env] in
+        let result = Sx_ref.eval_expr render_call (Env env) in
+        match result with
+        | String s | RawHTML s -> s
+        | _ -> Sx_runtime.value_to_str result
+      end else
+        Sx_render.render_to_html_streaming shell_call env
+    in
     let t4 = Unix.gettimeofday () in
     Printf.eprintf "[sx-http] %s route=%.3fs aser=%.3fs ssr=%.3fs shell=%.3fs total=%.3fs html=%d\n%!"
       path (t1 -. t0) (t2 -. t1) (t3 -. t2) (t4 -. t3) (t4 -. t0) (String.length html);
@@ -1733,9 +1746,7 @@ let http_inject_shell_statics env static_dir sx_sxc =
     (String.length pages_sx)
     (List.length (String.split_on_char '\n' pages_sx));
   ignore (env_bind env "__shell-pages-sx" (String pages_sx));
-  (* Add CSS to hide island placeholder SX text until client hydrates *)
+  ignore (env_bind env "__shell-sx-css" (String sx_css));
-  let island_css = "[data-sx-island]{font-size:0;line-height:0;overflow:hidden;max-height:0}" in
-  ignore (env_bind env "__shell-sx-css" (String (sx_css ^ "\n" ^ island_css)));
   ignore (env_bind env "__shell-sx-css-classes" (String ""));
   ignore (env_bind env "__shell-asset-url" (String "/static"));
   ignore (env_bind env "__shell-sx-js-hash" (String sx_js_hash));