feat: files pane like VS Code: tree, tabs, go to file

- Explorer tree with inline expand/collapse and keyboard navigation, git
  colours, change dots, dimmed gitignored entries (fs-list now flags them),
  file-type badges, resizable explorer.
- Editor tabs: preview tab semantics, instant switching with scroll kept,
  in-place reload when Claude changes an open file.
- Go to file: devdesk attach --fs-find (git ls-files or capped find) and a
  fuzzy-ranked palette (CommandPalette gained custom search/async lists).
- Per-session memory of folders and tabs; empty state with recents.

Closes #37

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

debian/changelog

@@ -1,3 +1,23 @@
+devdesk (0.7.1) bookworm; urgency=medium
+
+  * Files pane reworked like VS Code (#37):
+    - Explorer tree beside the editor: folders expand in place (also with
+      the keyboard: arrows, Enter), the open file is highlighted and can be
+      revealed, git colours on names, change dots on folders, gitignored
+      entries dimmed, file-type badges. A drag handle sizes the explorer.
+    - Tabs: a click opens a preview tab (italic) that the next click
+      replaces; double-click or Enter keeps it. Switching tabs is instant and
+      keeps the scroll position. Files Claude changes reload in place.
+    - Go to file (Ctrl+P in the pane, the ⌕ button, the palette): fuzzy
+      search over git ls-files, or a capped find outside git.
+    - Explorer and Changes are two views of the left column; diffs open as
+      tabs.
+    - Expanded folders, open tabs and the active tab are remembered per
+      session; an empty editor offers recent files and the change count.
+    - Narrow panes and phones: the explorer slides over the editor.
+
+ -- Jared Vititoe <jjvititoe1@gmail.com>  Thu, 08 Oct 2026 01:40:47 -0400
+
 devdesk (0.7.0) bookworm; urgency=medium
 
   * Files pane (#19): a Files button (Ctrl+Shift+E) next to Panels opens the