Cut the cost of finding what a selection box contains

A window over a whole drawing spent 407 ms gathering candidates and 259 ms
testing them, of 825 ms total, at 186 468 entities.

**Gathering** ran eight spatial queries because that is what hover and
snapping need between them. An area selection reads five: the wires and their
segments, plus the fill triangles, pick triangles and glyphs that
`indexed_box_crossing_hits` uses to catch hatches and text inside the box.
The three that exist only for snapping are skipped.

That was worth 148 ms. The rest came from the queries themselves.
`SpatialGrid::query` sorts its result twice — once over the entry indices, to
remove the repeats an entry collects for spanning several cells, and once
over the values. Over a box covering the drawing that is two O(n log n)
passes across 4.4 M elements to remove a handful of duplicates.
`query_unordered` returns the same set in cell order with the duplicates left
in, and reserves the space it needs instead of growing a 17 MB vector in
steps. Gathering went from 515 ms to 69 ms on a synthetic set at that size,
and from 407 ms to 27-40 ms in the application.

Everything an area selection does with the result already dedups and does not
read the order. Click picking keeps the sorted `query`, where scan order
decides which of two overlapping entities a click lands on.

**Testing** projected both endpoints of every segment in the box, then threw
the result away for any wire already selected. A circle or a polyline
contributes one segment per tessellated span, so at 24 spans per wire that is
23 projection pairs out of 24 doing nothing. Skipping a wire once it is in
took a 4.4 M-segment scan from roughly a second to 42 ms.

The overlay path — active after any edit, so most of a working session —
needed the same treatment, including its own merge: `extend_indexed` sorts
and dedups every category, which would have put back the sorts this removes.
`extend_indexed_area` keeps the dedup on `wire_indices`, and must: the window
branch of `box_hit` walks it directly, so a wire left in twice would be
selected twice.

Tests cover the equivalence in both directions: the area query matches the
full one as a set in every category an area selection reads, and the merge
dedups `wire_indices` and nothing else.

src/app/update/viewport.rs

@@ -4186,8 +4186,9 @@ impl OpenCADStudio {
                         self.refresh_properties();
                         if crate::perf::enabled() {
                             crate::perf_record!(
-                                "[perf] select-commit kind=drag-box candidates={cand_ms:.1}ms \
-hit={hit_ms:.1}ms apply={apply_ms:.1}ms properties={:.1}ms picked={}",
+                                "[perf] select-commit kind=drag-box crossing={crossing} \
+candidates={cand_ms:.1}ms hit={hit_ms:.1}ms apply={apply_ms:.1}ms \
+properties={:.1}ms picked={}",
                                 t_props.map_or(0.0, |t| t.elapsed().as_secs_f64() * 1000.0),
                                 handles.len(),
                             );
@@ -4564,8 +4565,9 @@ hit={hit_ms:.1}ms apply={apply_ms:.1}ms properties={:.1}ms picked={}",
                     self.refresh_properties();
                     if crate::perf::enabled() {
                         crate::perf_record!(
-                            "[perf] select-commit kind=window candidates={cand_ms:.1}ms \
-hit={hit_ms:.1}ms filter={filter_ms:.1}ms apply={apply_ms:.1}ms properties={:.1}ms picked={}",
+                            "[perf] select-commit kind=window crossing={crossing} \
+candidates={cand_ms:.1}ms hit={hit_ms:.1}ms filter={filter_ms:.1}ms \
+apply={apply_ms:.1}ms properties={:.1}ms picked={}",
                             t_props.map_or(0.0, |t| t.elapsed().as_secs_f64() * 1000.0),
                             handles.len(),
                         );