Fix for EDT violations and other small fixes. - #45

1. QuadTreeRect.borderDistanceSqr: returned distance^4 (dx^2 squared again) instead of distance^2, causing incorrect nearest-neighbor pruning
2. QuadTreeNode.split: children were created without propagating minSize, defeating depth limits on dense data
3. QuadTreeNode.split: raw Collection<QuadTreeLeaf> replaced with parameterized Collection<QuadTreeLeaf<T>>
4. QuadTreeNode.remove: used == (identity) instead of Objects.equals(), failing for equal-but-not-same-instance objects
5. QuadTree.get: approximately_equal(west, east, .001) treated narrow bounding boxes as dateline crossings, returning global results

…patialIndex

Two defects made a layer lose its tooltip to layers below:

1) mouseMoved(MouseEvent): once the cursor rested on a filled graphic
   (OMRasterObject is always filled) every subsequent event took the
   mouse-timer branch, which returned false without consuming - so the
   MouseDelegator handed the event to lower layers, whose tooltip then
   overwrote this layer's. Now the timer branch only runs while the
   cursor is still over the tracked geometry (new stillOver(), same <4px
   tolerance as findClosest) and returns consumeEvents; on exit the
   timer is stopped and updateMouseMoved decides in the same dispatch.

2) mouseMoved() (consumed-by-other notification) called mouseNotOver(),
   whose handleToolTip(null) -> fireHideToolTip() cleared the tooltip
   the consuming layer had just set (InformationDelegator cannot tell
   who a hide comes from). Now it unhighlights, forgets lastToolTip,
   stops any pending timer (stale re-fire race) and drops the interest
   without hiding.

Also handleToolTip() now hides on a null->null transition so a leftover
tooltip from a lower layer cannot keep showing over a consuming graphic
that has no tooltip text of its own.

Verified with dk.navicon.openmap.kml.layer.test.TestKmlTooltipVsLayerAbove
(openmap-kml r72726). Version bumped to 5.1.21, deployed to nexus.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>