feat: add JSON-RPC client with connection check command

noise.el

@@ -11,6 +11,8 @@
 
 ;;; Code:
 
+(require 'noise-rpc)
+
 (defgroup noise nil
   "Signal Messenger client for Emacs."
   :group 'comm
@@ -22,6 +24,16 @@ Format: http://HOST:PORT"
   :type 'string
   :group 'noise)
 
+;;;###autoload
+(defun noise-check-connection ()
+  "Check connectivity to the signal-cli JSON-RPC daemon."
+  (interactive)
+  (condition-case err
+      (let ((version (noise-rpc-check)))
+        (message "signal-cli connected (version %s)" version))
+    (noise-rpc-error
+     (message "Error: %s" (cdr err)))))
+
 ;;;###autoload
 (define-minor-mode noise-mode
   "Toggle Noise Signal client mode."