feat(gui): docked details pane on wide windows

An adw::Breakpoint at 1000sp uncollapses the details OverlaySplitView, so
the pane sits beside the files instead of over them. The pane gains
Sharing and Versions sections, filled from ListShare and ListRevisions
when an entry is selected, with Share…, Copy Link and Versions… buttons.

docs/CHANGELOG.md

@@ -74,6 +74,10 @@ Schema: **31** (unchanged).
   application to use.
 - **One selection in My Files.** The grid and the list share their selection, so switching views
   keeps what is selected, and dragging across empty space draws a selection box in both.
+- **Details pane.** On a window at least 1000 px wide the details pane docks beside the files
+  instead of covering them. It has Info, Offline, Sharing and Versions sections: who has access or
+  whether there is a public link, how many versions there are, and Share…, Copy Link and
+  Versions… buttons.
 - **US spelling throughout.** The app, the CLI and the docs say "Favorite" and "color", matching the
   `pdfs favorite` command.