Uncommitted sx-tools changes: WASM bundles, Playwright specs, engine fixes

WASM browser bundles rebuilt with latest kernel. Playwright test specs
updated (helpers, navigation, handler-responses, hypermedia-handlers,
isomorphic, SPA navigation). Engine/boot/orchestration SX files updated.
Handler examples and not-found page refreshed.

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

hosts/ocaml/lib/sx_primitives.ml

@@ -687,6 +687,17 @@ let () =
     match args with
     | [SxExpr s] -> String s
     | [RawHTML s] -> String s
+    | [Spread pairs] ->
+      (* Serialize spread values as (make-spread {:key "val" ...}) *)
+      let dict_parts = List.map (fun (k, v) ->
+        Printf.sprintf ":%s %s" k (inspect v)) pairs in
+      String (Printf.sprintf "(make-spread {%s})" (String.concat " " dict_parts))
+    | [Component c] ->
+      (* Serialize component values as their ~name reference *)
+      String (Printf.sprintf "~%s" c.c_name)
+    | [Island i] ->
+      String (Printf.sprintf "~%s" i.i_name)
+    | [Lambda _] -> String "<lambda>"
     | [a] -> String (inspect a)  (* used for dedup keys in compiler *)
     | _ -> raise (Eval_error "serialize: 1 arg"));
   register "make-symbol" (fun args ->