Wire browsing a user's shared files into the TUI as a modal tree popup:
- press 'b' on a highlighted search result to browse that result's owner, or
'b' elsewhere to type a username (new CommandBarMode::Browse);
- a new models/browse.rs synthesizes the flat SharedDirectory list into a
nested, collapsible tree (intermediate folders reconstructed from the
backslash paths; file download paths kept byte-exact from the original names),
with expand/collapse state and a flatten-to-rows renderer — fully unit-tested;
- the popup polls take_browse_result each tick (with a timeout), navigates with
arrows/hjkl, expands/collapses folders, and queues downloads: Enter on a file,
'd' on a file or an entire folder subtree (recursively) — all funneled into
the existing Downloads pane;
- shortcuts bar advertises browse keys and surfaces our own sharing status.
Splits the downloads area 60/40 with a new info pane that adapts to the
selected download's status: header (filename, user, size, status, save
path, bitrate, length) plus queued-specific fields (queue position, peer
slots, peer upload speed) or live progress/speed/ETA when transferring.
Plumbs queue position via a new ClientOperation::PlaceInQueueUpdate so
PlaceInQueueResponse messages from peers reach DownloadStore, and threads
search-time metadata (bitrate, length, peer slots/speed) onto Download
through a new download_with_metadata entry point.
michel