Command line: hovered history lines stay until the pointer leaves

Lines still showing when the pointer reaches the overlay history no
longer fade under it; leaving restarts their COMMANDLINEFADETIME.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/mod.rs

@@ -3059,6 +3059,8 @@ pub enum Message {
     /// User clicked a command-line option button — feed its keyword to the
     /// active command as if typed (empty keyword = Enter). (#304)
     CommandOptionPick(String),
+    /// The pointer entered (true) or left the command line's overlay history.
+    CommandHistoryHover(bool),
     ToggleLayers,
     /// Open/focus (or close) the Reference Manager palette.
     ToggleXrefManager,