File tree in the right sidebar: four additions it already has room for

[devacc8]

The ui-sidebar-files tree covers the main case well, and its own docs list what is still deferred ("Listing only. No search, artifact filter ... no current-file highlight"; "a reload starts every session collapsed"). Four additions that stay inside the current design rather than changing it. All four are used daily in a community plugin, so the behaviour is field-tested rather than theoretical.

1. File-type icons in the rows.
FileTypeIcon already exists and the tab chip uses it, but the tree's own rows never draw it. A 200-entry listing is much faster to scan when markdown, code, JSON, style, data, shell and image files are distinguishable before reading the name. A per-family shade taken from a token keeps light and dark correct.

2. A filter box above the tree.
Client-side and name-only over the levels already listed, with a Host fallback for deeper matches if that is worth the round trip. Typing three letters beats collapsing folders by hand, and it composes with the existing lazy listing.

3. Highlight the file the pane is showing.
When a file is opened, from the tree or through a resource link, select its row and scroll it into view. Today the tree gives no clue which file the pane holds, which starts to matter once several folders are expanded.

4. Persist expansion and scroll.
"Memory-only. Nothing is persisted; a reload starts every session collapsed." Storing expanded plus one scroll offset per session id in localStorage would make a reload feel like nothing happened. Smallest change of the four, probably the largest perceived win.

Optional and larger: sorting by size or modified time needs mtime in the listing payload, so it is an API question before it is a UI one. The current ordering (directories first, then natural case-insensitive name) is a fine default.

A reference implementation of 1 to 4 (plus in-panel editing, which the read-only service deliberately does not offer), MIT licensed: https://github.com/devacc8/dsh-file-explorer

Not asking for a commitment. Leaving the notes where they are easy to find.