fix(hover): defer rollover pick until the cursor stops

The rollover hit-test now sweeps wires, hatches, block-internal hatches
and shaded solid bodies, which is O(N) per cursor frame and was freezing
the crosshair on large drawings. Each idle move now clears the live
highlight and arms a dwell timer; HoverDwellTick runs the pick once the
cursor has been still for HOVER_DWELL_MS (120 ms), using the active
tile's bounds so the deferred pick matches the entity actually under
the cursor in tiled viewports.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/view.rs

@@ -1623,6 +1623,14 @@ impl OpenCADStudio {
         } else {
             Subscription::none()
         };
+        // While a rollover pick is queued, drive ticks so it fires the
+        // moment the cursor has been still for the dwell window — without
+        // this `ViewportMove` alone never re-fires once the user stops.
+        let hover_dwell = if self.hover_dwell.is_some() {
+            window::frames().map(|_| Message::HoverDwellTick)
+        } else {
+            Subscription::none()
+        };
         // Blink the MText preview caret while the editor is open.
         let caret_blink = if self.mtext_editor.is_some() {
             iced::time::every(std::time::Duration::from_millis(530))
@@ -1642,6 +1650,7 @@ impl OpenCADStudio {
             frames,
             history_tick,
             grip_dwell,
+            hover_dwell,
             caret_blink,
             web_fonts,
             event::listen_with(|ev, status, win_id| {