Files · Transfers: file operations, a transfer queue, downloads and storage

A file on its way is a Transfer with a state: waiting, moving at a rate,
paused, done or failed with a reason. One row draws it for the queue and
the downloads: its icon, its way, a bar while it moves or waits paused, a
status with the time left, and only the actions its state allows.
TransferQueue counts what moves and waits. DownloadManager keeps the
finished below under Clear, opening on a press and showing their folder.
FileOperationProgress tells a copy or move with its bar, time left and
current file, its header wrapping by the header rule; a failure speaks in
the danger tone. StorageUsage points to data_display's UsageBar.

src/files/mod.rs

@@ -11,9 +11,12 @@ mod explorer;
 mod grid;
 mod icon;
 mod item;
+mod operation;
 mod preview;
 mod recent;
 mod search;
+mod transfer;
+mod transfers;
 
 type OnEntry = Rc<dyn Fn(&DirEntry, &mut Window, &mut App)>;
 
@@ -26,6 +29,9 @@ pub use explorer::{FileExplorer, FileView};
 pub use grid::FileGrid;
 pub use icon::FileIcon;
 pub use item::FileItem;
+pub use operation::{FileOperation, FileOperationProgress};
 pub use preview::FilePreview;
 pub use recent::{RecentFile, RecentFiles};
 pub use search::{FileSearch, FoundFile};
+pub use transfer::{Transfer, TransferState};
+pub use transfers::{DownloadManager, TransferQueue};