Fix JIT compiler, CSSX browser support, double-fetch, SPA layout

JIT compiler:
- Fix jit_compile_lambda: resolve `compile` via symbol lookup in env
  instead of embedding VmClosure in AST (CEK dispatches differently)
- Register eval-defcomp/eval-defisland/eval-defmacro runtime helpers
  in browser kernel for bytecoded defcomp forms
- Disable broken .sxbc.json path (missing arity in nested code blocks),
  use .sxbc text format only
- Mark JIT-failed closures as sentinel to stop retrying

CSSX in browser:
- Add cssx.sx symlink + cssx.sxbc to browser web stack
- Add flush-cssx! to orchestration.sx post-swap for SPA nav
- Add cssx.sx to compile-modules.js and mcp_tree.ml bytecode lists

SPA navigation:
- Fix double-fetch: check e.defaultPrevented in click delegation
  (bind-event already handled the click)
- Fix layout destruction: change nav links from outerHTML to innerHTML
  swap (outerHTML destroyed #main-panel when response lacked it)
- Guard JS popstate handler when SX engine is booted
- Rename sx-platform.js → sx-platform-2.js to bust immutable cache

Playwright tests:
- Add trackErrors() helper to all test specs
- Add SPA DOM comparison test (SPA nav vs fresh load)
- Add single-fetch + no-duplicate-elements test
- Improve MCP tool output: show failure details and error messages

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

hosts/ocaml/bin/mcp_tree.ml

@@ -606,6 +606,7 @@ let rec handle_tool name args =
       "render.sx"; "core-signals.sx"; "signals.sx"; "deps.sx"; "router.sx";
       "page-helpers.sx"; "freeze.sx"; "bytecode.sx"; "compiler.sx"; "vm.sx";
       "dom.sx"; "browser.sx"; "adapter-html.sx"; "adapter-sx.sx"; "adapter-dom.sx";
+      "cssx.sx";
       "boot-helpers.sx"; "hypersx.sx"; "harness.sx"; "harness-reactive.sx";
       "harness-web.sx"; "engine.sx"; "orchestration.sx"; "boot.sx";
     ] in
@@ -1225,18 +1226,41 @@ let rec handle_tool name args =
       (try while true do lines := input_line ic :: !lines done with End_of_file -> ());
       ignore (Unix.close_process_in ic);
       let all_lines = List.rev !lines in
-      let fails = List.filter (fun l -> let t = String.trim l in
-        String.length t > 1 && (t.[0] = '\xE2' (* ✘ *) || (String.length t > 4 && String.sub t 0 4 = "FAIL"))) all_lines in
+      (* Count passed/failed/skipped from the summary line *)
       let summary = List.find_opt (fun l ->
         try let _ = Str.search_forward (Str.regexp "passed\\|failed") l 0 in true
         with Not_found -> false) (List.rev all_lines) in
-      let result = match summary with
-        | Some s ->
-          if fails = [] then s
-          else s ^ "\n\nFailures:\n" ^ String.concat "\n" fails
-        | None ->
-          let last_n = List.filteri (fun i _ -> i >= List.length all_lines - 10) all_lines in
-          String.concat "\n" last_n
+      (* Extract test names that failed *)
+      let fail_names = List.filter_map (fun l ->
+        let t = String.trim l in
+        if String.length t > 2 then
+          try
+            let _ = Str.search_forward (Str.regexp "› .* › ") t 0 in
+            Some ("  " ^ t)
+          with Not_found -> None
+        else None) all_lines in
+      (* Extract error messages (lines starting with Error:) *)
+      let errors = List.filter_map (fun l ->
+        let t = String.trim l in
+        if String.length t > 6 then
+          try
+            let _ = Str.search_forward (Str.regexp "expect.*\\(received\\)\\|Expected\\|Received\\|Error:.*expect") t 0 in
+            Some ("    " ^ t)
+          with Not_found -> None
+        else None) all_lines in
+      let total = List.length fail_names + (match summary with
+        | Some s -> (try let _ = Str.search_forward (Str.regexp "\\([0-9]+\\) passed") s 0 in
+            int_of_string (Str.matched_group 1 s) with _ -> 0)
+        | None -> 0) in
+      let summary_str = match summary with Some s -> String.trim s | None -> "no summary" in
+      let result =
+        if fail_names = [] then
+          Printf.sprintf "%s (%d total)" summary_str total
+        else
+          Printf.sprintf "%s (%d total)\n\nFailed:\n%s\n\nErrors:\n%s"
+            summary_str total
+            (String.concat "\n" fail_names)
+            (String.concat "\n" (List.filteri (fun i _ -> i < 10) errors))
       in
       text_result result
     end else begin