Fix delete-row handler: nested slug extraction in OCaml dispatch

The slug extractor after (api. scanned for the first ) but for nested
URLs like (api.(delete.1)) it got "(delete.1" instead of "delete".
Now handles nested parens: extracts handler name and injects path
params into query string. Also strengthened the Playwright test to
accept confirm dialogs and assert strict row count decrease.

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

hosts/ocaml/bin/sx_server.ml

@@ -2658,8 +2658,29 @@ let http_mode port =
                   if i + 5 > String.length s then ""
                   else if String.sub s i 5 = "(api." then
                     let start = i + 5 in
-                    let end_ = try String.index_from s start ')' with Not_found -> String.length s in
-                    String.sub s start (end_ - start)
+                    if start < String.length s && s.[start] = '(' then
+                      (* Nested: (api.(delete.1)) — extract "delete" as slug,
+                         inject path param into query string *)
+                      let inner = start + 1 in
+                      let end_ =
+                        let rec scan j =
+                          if j >= String.length s then j
+                          else match s.[j] with '.' | ')' -> j | _ -> scan (j + 1)
+                        in scan inner in
+                      let handler_name = String.sub s inner (end_ - inner) in
+                      (* Extract path param value if present (after the dot) *)
+                      if end_ < String.length s && s.[end_] = '.' then begin
+                        let val_start = end_ + 1 in
+                        let val_end = try String.index_from s val_start ')' with Not_found -> String.length s in
+                        let param_val = String.sub s val_start (val_end - val_start) in
+                        (* Append to query string so request-arg can find it *)
+                        let sep = if !_req_query = "" then "" else "&" in
+                        _req_query := !_req_query ^ sep ^ "item-id=" ^ param_val
+                      end;
+                      handler_name
+                    else
+                      let end_ = try String.index_from s start ')' with Not_found -> String.length s in
+                      String.sub s start (end_ - start)
                   else find_api s (i + 1) in
                 find_api path 0 in
               let handler_key = "handler:ex-" ^ slug in