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/server_posix.go

@@ -0,0 +1,21 @@
+//go:build !windows
+// +build !windows
+
+package sftp
+
+import (
+	"io/fs"
+	"os"
+)
+
+func (s *Server) openfile(path string, flag int, mode fs.FileMode) (file, error) {
+	return os.OpenFile(path, flag, mode)
+}
+
+func (s *Server) lstat(name string) (os.FileInfo, error) {
+	return os.Lstat(name)
+}
+
+func (s *Server) stat(name string) (os.FileInfo, error) {
+	return os.Stat(name)
+}