Panel now enters archives (.tar, .tar.gz, .tar.bz2, .tar.xz, .zip,
.cpio) when pressing Enter, browsing their contents like directories.
Pressing '..' at the archive root exits back to the local filesystem.
Three new Panel fields: vfs (Box<dyn Vfs> backend), vfs_path (VfsPath
inside archive), vfs_archive (local PathBuf of archive file).
New methods: try_enter_archive(), replace_directory_vfs(),
display_path(), is_in_vfs(), is_archive_extension() helper.
Title bar shows 'archive.tar:/inner/path' when browsing inside an
archive via synthesized display path.
5 new tests for archive extension detection (case-insensitive).
964 tests total, 0 failures.
vasilito
fde8384189