Inline test runner: 5/5 temperature converter tests passing

Fixed three fundamental issues:
1. cek-try arg passing: handler was called with raw string instead of
   (List [String msg]), causing "lambda expects 1 args, got N" errors
2. Silent island hydration failures: hydrate-island now wraps body
   render in cek-try, displaying red error box with stack trace instead
   of empty div. No more silent failures.
3. swap! thunk leak: apply result wasn't trampolined, storing thunks
   as signal values instead of evaluated results

Also fixed: assert= uses = instead of equal? for value comparison,
assert-signal-value uses deref instead of signal-value, HTML entity
decoding in script tag test source via host-call replaceAll.

Temperature converter demo page now shows live test results:
  ✓ initial celsius is 20
  ✓ computed fahrenheit = celsius * 1.8 + 32
  ✓ +5 increments celsius
  ✓ fahrenheit updates on celsius change
  ✓ multiple clicks accumulate

1116/1116 OCaml tests pass.

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

hosts/ocaml/bin/run_tests.ml

@@ -65,7 +65,18 @@ let make_test_env () =
     ignore (Sx_types.env_bind env name (NativeFn (name, fn)))
   in
 
-  (* --- 5 platform functions required by test-framework.sx --- *)
+  (* --- platform functions required by test-framework.sx --- *)
+
+  bind "cek-try" (fun args ->
+    match args with
+    | [thunk; handler] ->
+      (try Sx_ref.cek_call thunk Nil
+       with Eval_error msg -> Sx_ref.cek_call handler (List [String msg]))
+    | [thunk] ->
+      (try let r = Sx_ref.cek_call thunk Nil in
+        List [Symbol "ok"; r]
+       with Eval_error msg -> List [Symbol "error"; String msg])
+    | _ -> Nil);
 
   bind "try-call" (fun args ->
     match args with

hosts/ocaml/bin/sx_server.ml

@@ -389,7 +389,7 @@ let setup_evaluator_bridge env =
     match args with
     | [thunk; handler] ->
       (try Sx_ref.cek_call thunk Nil
-       with Eval_error msg -> Sx_ref.cek_call handler (String msg))
+       with Eval_error msg -> Sx_ref.cek_call handler (List [String msg]))
     | [thunk] ->
       (try let r = Sx_ref.cek_call thunk Nil in
         List [Symbol "ok"; r]

hosts/ocaml/browser/sx_browser.ml

@@ -481,7 +481,7 @@ let () =
     match args with
     | [thunk; handler] ->
       (try Sx_ref.cek_call thunk Nil
-       with Eval_error msg -> Sx_ref.cek_call handler (String msg))
+       with Eval_error msg -> Sx_ref.cek_call handler (List [String msg]))
     | [thunk] ->
       (try let r = Sx_ref.cek_call thunk Nil in
         List [Symbol "ok"; r]