SSH connection status indicators

- Add Connected bool field to vfs.Entry and RemoteMount
- Track connection status in sshState.connectedHosts
- Show status icon (connected/disconnected) in pane header when browsing remote host
- Async SSH connection test with cancel support for Add Host dialog
- Colored labels and styled help text in SSH dialogs
- Confirmation dialog when deleting manually-added SSH hosts

vendor/github.com/pkg/sftp/SECURITY.md

@@ -0,0 +1,13 @@
+# Security Policy
+
+## Supported Versions
+
+Security updates are provided for the latest released version of this package.
+We also welcome vulnerability reports for the development version to help us ensure it is secure before the next release.
+
+## Reporting a Vulnerability
+
+If you believe you’ve found a security vulnerability in this project, we strongly encourage you to report it privately using GitHub’s [security advisory system](https://github.com/pkg/sftp/security/advisories/new).
+This will allow us to review and address the issue before public disclosure.  
+
+Thank you for helping us keep the project secure.