fix: add sudo fallback to agent installer + improve error output

- AgentService: try sudo -n first, fall back to bash without sudo
- AgentService: add sudo to uninstall command
- AgentService: trim error output to last 20 lines for readability
- View: show SSH output inline in error toast
- Fix undefined $path variable in success path

views/servers/show.php

@@ -445,8 +445,9 @@ function confirmAgentAction() {
             showToast('success', action === 'install' ? 'Agent installed successfully.' : 'Agent uninstalled successfully.');
             setTimeout(() => location.reload(), 1500);
         } else {
-            showToast('error', data.error || (action === 'install' ? 'Installation failed.' : 'Uninstallation failed.'));
-            if (data.output) console.log('Output:', data.output);
+            let msg = data.error || (action === 'install' ? 'Installation failed.' : 'Uninstallation failed.');
+        if (data.output) msg += ' Output: ' + data.output.replace(/\n/g, ' | ');
+        showToast('error', msg);
         }
     })
     .catch(err => {