Dock: review cleanups - hover pending enum, FloatFrame, comment fixes

- dock_hover_pending is an Option<HoverPending> (Reveal / Hide) instead
  of a nested Option.
- dock_float_frame returns a FloatFrame with width() and bar_x(), so the
  floating menu no longer repeats the frame-width formula.
- Put dock_reveal's doc comment back on dock_reveal, and the group-move
  comment back above the match it describes.

No behaviour change.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_013RyGiMXcsf9HTKfqDxaQGt

src/ui/dock.rs

@@ -86,6 +86,15 @@ pub enum DockMsg {
     HoverSettled(u64),
 }
 
+/// An auto-hide change waiting out [`DOCK_HOVER_DELAY`].
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum HoverPending {
+    /// Reveal this pallet (its group, or its floating frame).
+    Reveal(PanelId),
+    /// Hide whatever auto-hiding pallet is revealed.
+    Hide,
+}
+
 /// How long the pointer must rest before an auto-hiding group reveals or
 /// hides, so passing over the strip doesn't flash groups open.
 pub const DOCK_HOVER_DELAY: std::time::Duration = std::time::Duration::from_millis(150);