feat: enhance error handling in OAuth URL building and client creation; improve tool argument sanitization

src/service/oauth/manager.rs

@@ -84,7 +84,22 @@ impl OAuthManager {
     }
 
     pub fn build_auth_url(&self, redirect_uri: &str, state: &str, code_challenge: &str) -> String {
-        let mut url = url::Url::parse(&self.config.auth_url).unwrap_or_else(|_| url::Url::parse("https://example.com").unwrap());
+        // Refuse to build a URL if `auth_url` is missing or invalid. Previously this
+        // silently fell back to https://example.com, which produced a valid-looking
+        // auth URL pointing at the wrong server and leaked client credentials in
+        // query params. Returning an empty string signals failure to callers, who
+        // can prompt the user to fix the OAuth config instead of starting a flow
+        // against a wrong host.
+        let mut url = match url::Url::parse(&self.config.auth_url) {
+            Ok(u) if !self.config.auth_url.is_empty() => u,
+            _ => {
+                eprintln!(
+                    "warning: OAuth auth_url is missing or invalid ('{}'); aborting build_auth_url",
+                    self.config.auth_url
+                );
+                return String::new();
+            }
+        };
         url.query_pairs_mut()
             .append_pair("response_type", "code")
             .append_pair("client_id", &self.config.client_id)