fix: use correct signal-cli default port 8080 and robust connectivity check

- Change default noise-signal-cli-address to port 8080 (signal-cli's --http default)
- Replace getVersion (not a valid JSON-RPC method) with noisePing probe
- noise-rpc-check now returns t on any valid JSON-RPC response
- Update README to reflect correct default port

noise.el

@@ -19,9 +19,10 @@
   :group 'comm
   :prefix "noise-")
 
-(defcustom noise-signal-cli-address "http://localhost:9128"
+(defcustom noise-signal-cli-address "http://localhost:8080"
   "Base URL of the signal-cli JSON-RPC daemon.
-Format: http://HOST:PORT"
+Format: http://HOST:PORT
+The default port is 8080, matching signal-cli's `--http` default."
   :type 'string
   :group 'noise)
 
@@ -30,8 +31,9 @@ Format: http://HOST:PORT"
   "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))
+      (progn
+        (noise-rpc-check)
+        (message "signal-cli connected at %s" noise-signal-cli-address))
     (noise-rpc-error
      (message "Error: %s" (cdr err)))))