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.

AGENTS.md

@@ -113,6 +113,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - gpui 0.2.2's `line_clamp` wraps once and lays the rest on the last line, cut hard; centered, it loses both ends. A name whose ends matter is a `typography::MiddleEllipsis` on one line (`files::FileGrid`).
 - Set an explicit line height on any box that clips text. gpui's default leading is taller than a tight box, and the clip eats descenders.
 - gpui's `img` takes its picture's pixel size for any `Auto` side, and its aspect ratio beats percent heights in flow. `Image` pins it absolute at full size, so an `Image` needs a sized box.
+- A file on its way is a `files::Transfer` drawn by one row in `files::transfer`: TransferQueue and DownloadManager share it, and its actions follow its state.
 - Paths with `/` between folders become a tree through `lists::Folder::of`, for `FileTree` and `files::ArchiveViewer` alike.
 - A folder's path over its entries is `lists::path_bar`, and its first order is `lists::listed`, folders first by name: DirectoryListing and FileExplorer share both, so every view shows one path and one order.
 - A file's icon comes from `primitives::file_icon`, one map from name to icon for every chapter; `files::FileIcon` draws it. What fits across a width comes from `layout::columns_for`, and `layout::fit` adds the inset that centers it.