Fix WASM browser: broken links (&rest bytecode) + broken reactive counter (ListRef mutation)

Two bugs fixed:

1. Links: bytecode compiler doesn't handle &rest params — treats them as
   positional, so (first rest) gets a raw string instead of a list.
   Replaced &rest with explicit optional params in all bytecode-compiled
   web SX files (dom-query, dom-add-listener, browser-push-state, etc.).
   The VM already pads missing args with Nil.

2. Reactive counter: signal-remove-sub! used (filter ...) which returns
   immutable List, but signal-add-sub! uses (append!) which only mutates
   ListRef. Subscribers silently vanished after first effect re-run.
   Fixed by adding remove! primitive that mutates ListRef in-place.

Also:
- Added evalVM API to WASM kernel (compile + run through bytecode VM)
- Added scope tracing (scope-push!/pop!/peek/context instrumentation)
- Added Playwright reactive mode for debugging island signal/DOM state
- Replaced cek-call with direct calls in core-signals.sx effect/computed
- Recompiled all 23 bytecode modules

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

hosts/ocaml/lib/sx_scope.ml

@@ -12,6 +12,16 @@ open Sx_types
     Used by aser for spread/provide/emit patterns, CSSX collect/flush, etc. *)
 let scope_stacks : (string, value list) Hashtbl.t = Hashtbl.create 8
 
+(** Debug trace for scope operations — enabled from JS *)
+let _scope_trace = ref false
+let _scope_log : string list ref = ref []
+let scope_trace_enable () = _scope_trace := true; _scope_log := []
+let scope_trace_disable () = _scope_trace := false
+let scope_trace_drain () =
+  let log = List.rev !_scope_log in
+  _scope_log := [];
+  log
+
 (** Request cookies — set by the Python bridge before each render.
     get-cookie reads from here; set-cookie is a no-op on the server. *)
 let request_cookies : (string, string) Hashtbl.t = Hashtbl.create 8
@@ -40,6 +50,8 @@ let () =
     match args with
     | [String name; value] ->
       let stack = try Hashtbl.find scope_stacks name with Not_found -> [] in
+      if !_scope_trace then
+        _scope_log := Printf.sprintf "PUSH %s depth=%d->%d" name (List.length stack) (List.length stack + 1) :: !_scope_log;
       Hashtbl.replace scope_stacks name (value :: stack); Nil
     | _ -> Nil);
 
@@ -47,6 +59,8 @@ let () =
     match args with
     | [String name] ->
       let stack = try Hashtbl.find scope_stacks name with Not_found -> [] in
+      if !_scope_trace then
+        _scope_log := Printf.sprintf "POP %s depth=%d->%d" name (List.length stack) (max 0 (List.length stack - 1)) :: !_scope_log;
       (match stack with _ :: rest -> Hashtbl.replace scope_stacks name rest | [] -> ()); Nil
     | _ -> Nil);
 
@@ -54,6 +68,8 @@ let () =
     match args with
     | [String name] ->
       let stack = try Hashtbl.find scope_stacks name with Not_found -> [] in
+      if !_scope_trace then
+        _scope_log := Printf.sprintf "PEEK %s depth=%d found=%b" name (List.length stack) (stack <> []) :: !_scope_log;
       (match stack with v :: _ -> v | [] -> Nil)
     | _ -> Nil);
 
@@ -63,6 +79,8 @@ let () =
     match args with
     | [String name] | [String name; _] ->
       let stack = try Hashtbl.find scope_stacks name with Not_found -> [] in
+      if !_scope_trace then
+        _scope_log := Printf.sprintf "CTX %s depth=%d found=%b" name (List.length stack) (stack <> []) :: !_scope_log;
       (match stack, args with
        | v :: _, _ -> v
        | [], [_; default_val] -> default_val