perf: warm the entity quadtree alongside the handle index

Warming only the interaction handle index left the first hover at
385 ms, down from 992 but not gone:

    hover-detail  query=0.1 handles=384.6 ... candidates=186

The handles stage builds two indexes, not one. `interaction_candidate_handles`
also reaches for `entity_index()` — the entity quadtree, keyed on
geometry_epoch and just as cold at that point. Warm both.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/scene/mod.rs

@@ -7912,6 +7912,11 @@ impl Scene {
     /// already waiting. A second on an open that is already seconds long reads
     /// very differently from a second-long freeze on a mouse move.
     pub(crate) fn warm_interaction_caches(&self) {
+        // Both indexes on the hover path, not just one. The handle index alone
+        // left `hover-detail ... handles=384.6` on the first hover: the same
+        // stage also builds the entity quadtree, which is keyed on
+        // `geometry_epoch` and equally cold at that point.
+        let _ = self.entity_index();
         let _ = self.interaction_handle_index();
     }