fix: handle URLs already ending in /jsonrpc.php

NewClient() now detects when the provided URL already ends with
/jsonrpc.php and avoids appending it again. This prevents double-path
issues like /jsonrpc.php/jsonrpc.php.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client.go

@@ -29,9 +29,15 @@ func NewClient(baseURL string) *Client {
 	// Ensure no trailing slash
 	baseURL = strings.TrimSuffix(baseURL, "/")
 
+	// Handle URLs that already include /jsonrpc.php
+	endpoint := baseURL
+	if !strings.HasSuffix(baseURL, "/jsonrpc.php") {
+		endpoint = baseURL + "/jsonrpc.php"
+	}
+
 	c := &Client{
 		baseURL:  baseURL,
-		endpoint: baseURL + "/jsonrpc.php",
+		endpoint: endpoint,
 	}
 
 	c.httpClient = &http.Client{