tools: handle string 'true' for elevated flag

Kiro's bridge sends elevated as a string rather than a boolean.
Use a type switch to handle both cases.

pkg/tools/execute/server.go

@@ -287,8 +287,11 @@ func (e *Server) callPromotedTool(ctx context.Context, tool string, args json.Ra
 	var argMap map[string]interface{}
 	if err := json.Unmarshal(args, &argMap); err == nil {
 		if e, ok := argMap["elevated"]; ok {
-			if b, ok := e.(bool); ok {
-				elevated = b
+			switch v := e.(type) {
+			case bool:
+				elevated = v
+			case string:
+				elevated = v == "true" || v == "1"
 			}
 			// Remove elevated from the args passed to the tool.
 			delete(argMap, "elevated")