refactor(ui): side panels on craft-ui task panes and the shared rail (#4606)

* refactor(ui): side panels on craft-ui task panes and the shared rail

The Tools pane and the open side panel are docked craft-ui task panes
(craft_ui::panes::PaneHost, Columns policy, no title bars, not movable),
and the rail is craft_ui::panes::Rail with the page navigation cluster
as its foot. On the right, outermost first: the rail, Tools when
Preferences > Tools panel side is Right, the side panel, the page.
Read mode uses the same panes without Tools; All tools full view still
covers them. Floating, tab groups and drag-in are gone with docking.rs.

- Widths are resizable within the old limits and saved under a new
  side_panels preference (version 1) with the Tools side and open state.
  The old docking value is read once as plain JSON and dropped on save.
- ui.dock becomes ui.panel {panel: tools|side, open, width};
  ui.dock.reset resets the side panels ("Reset side panels").
- F4 shows or hides the side panel (reopening the last one) and
  Shift+F4 the Tools panel, as View menu commands.
- craft-ui pinned to e9630ae7 (craft-libs#309).

* fix(ui): side panels clippy lint and the dragged-width test's grab offset

* chore(deps): pin craft-ui at 7c42807, whose pane resize edges work over the page

* chore(deps): pin craft-ui at craft-libs main ea4c823, with panes::Rail

crates/engine/src/commands.rs

@@ -231,7 +231,23 @@ pub const COMMANDS: &[CommandSpec] = &[
     c("view.previous_view", "Previous view", None, Some(Shortcut::cmd("[")), Document, "chevron-left"),
     c("view.next_view", "Next view", None, Some(Shortcut::cmd("]")), Document, "chevron-right"),
     c("view.focus_page_input", "Go to page…", VIEW, Some(Shortcut::cmd_shift("N")), Document, "text-cursor-input"),
-    c("ui.dock.reset", "Reset panel layout", VIEW, None, Nothing, "settings"),
+    c(
+        "view.side_panel",
+        "Show or hide the side panel",
+        VIEW,
+        Some(Shortcut { command: false, shift: false, mac_ctrl: false, key: "F4" }),
+        Nothing,
+        "panel-right",
+    ),
+    c(
+        "view.tools_pane",
+        "Show or hide the Tools panel",
+        VIEW,
+        Some(Shortcut { command: false, shift: true, mac_ctrl: false, key: "F4" }),
+        Nothing,
+        "panel-left",
+    ),
+    c("ui.dock.reset", "Reset side panels", VIEW, None, Nothing, "settings"),
     c("view.theme", "Switch light / dark theme", None, None, Nothing, "moon"),
     c("view.theme.system", "Use system setting", None, None, Nothing, "settings"),
     c("view.theme.light", "Light gray", None, None, Nothing, "sun"),