SX renderer: adapter-html.sx as sole renderer, conditions, pattern matching

Evaluator: conditions/restarts, pattern matching, render-trace support.
adapter-html.sx: full SX-defined HTML renderer replacing native OCaml.
spec/render.sx: updated render mode helpers.
sx_browser.ml: use SX render-to-html instead of native.
sx_ref.ml: evaluator updates for conditions + match.
Bootstrap + transpiler updates for new forms.

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

hosts/ocaml/bootstrap.py

@@ -60,6 +60,9 @@ let _prim_param_types_ref = ref Nil
    run with hook = None (pure CEK, no compilation dependency). *)
 let jit_call_hook : (value -> value list -> value option) option ref = ref None
 
+(* Component trace — captures kont from last CEK error for diagnostics *)
+let _last_error_kont : value ref = ref Nil
+
 """
 
 
@@ -75,13 +78,58 @@ let () = trampoline_fn := (fun v ->
 (* Wire up the primitives trampoline so call_any in HO forms resolves Thunks *)
 let () = Sx_primitives._sx_trampoline_fn := !trampoline_fn
 
-(* Override recursive cek_run with iterative loop *)
+(* Override recursive cek_run with iterative loop.
+   On error, capture the kont from the last state for comp-trace. *)
 let cek_run_iterative state =
   let s = ref state in
-  while not (match cek_terminal_p !s with Bool true -> true | _ -> false) do
-    s := cek_step !s
+  (try
+    while not (match cek_terminal_p !s with Bool true -> true | _ -> false) do
+      s := cek_step !s
+    done;
+    cek_value !s
+  with Eval_error msg ->
+    _last_error_kont := cek_kont !s;
+    raise (Eval_error msg))
+
+(* Collect component trace from a kont value *)
+let collect_comp_trace kont =
+  let trace = ref [] in
+  let k = ref kont in
+  while (match !k with List (_::_) -> true | _ -> false) do
+    (match !k with
+     | List (frame :: rest) ->
+       (match frame with
+        | CekFrame f when f.cf_type = "comp-trace" ->
+          let name = match f.cf_name with String s -> s | _ -> "?" in
+          let file = match f.cf_env with String s -> s | Nil -> "" | _ -> "" in
+          trace := (name, file) :: !trace
+        | Dict d when (match Hashtbl.find_opt d "type" with Some (String "comp-trace") -> true | _ -> false) ->
+          let name = match Hashtbl.find_opt d "name" with Some (String s) -> s | _ -> "?" in
+          let file = match Hashtbl.find_opt d "file" with Some (String s) -> s | _ -> "" in
+          trace := (name, file) :: !trace
+        | _ -> ());
+       k := List rest
+     | _ -> k := List [])
   done;
-  cek_value !s
+  List.rev !trace
+
+(* Format a comp-trace into a human-readable string *)
+let format_comp_trace trace =
+  match trace with
+  | [] -> ""
+  | entries ->
+    let lines = List.mapi (fun i (name, file) ->
+      let prefix = if i = 0 then "  in " else "  called from " in
+      if file = "" then prefix ^ "~" ^ name
+      else prefix ^ "~" ^ name ^ " (" ^ file ^ ")"
+    ) entries in
+    "\n" ^ String.concat "\n" lines
+
+(* Enhance an error message with component trace *)
+let enhance_error_with_trace msg =
+  let trace = collect_comp_trace !_last_error_kont in
+  _last_error_kont := Nil;
+  msg ^ (format_comp_trace trace)
 
 
 
@@ -248,6 +296,24 @@ def compile_spec_to_ml(spec_dir: str | None = None) -> str:
         import sys
         print("WARNING: Could not find lambda body pattern for JIT injection", file=sys.stderr)
 
+    # Instrument recursive cek_run to capture kont on error (for comp-trace).
+    # The iterative cek_run_iterative already does this, but cek_call uses
+    # the recursive cek_run.
+    cek_run_old = (
+        'and cek_run state =\n'
+        '  (if sx_truthy ((cek_terminal_p (state))) then (cek_value (state)) else (cek_run ((cek_step (state)))))'
+    )
+    cek_run_new = (
+        'and cek_run state =\n'
+        '  (if sx_truthy ((cek_terminal_p (state))) then (cek_value (state)) else\n'
+        '   try cek_run ((cek_step (state)))\n'
+        '   with Eval_error msg ->\n'
+        '     (if !_last_error_kont = Nil then _last_error_kont := cek_kont state);\n'
+        '     raise (Eval_error msg))'
+    )
+    if cek_run_old in output:
+        output = output.replace(cek_run_old, cek_run_new, 1)
+
     return output