fix(hit_test): correct hatch selection — NaN-aware ray-cast + block-insert resolve

Two related click bugs:

1. `point_in_polygon` treated NaN points (the path separators used by
   multi-path hatches with islands / holes) as regular vertices,
   producing spurious closing edges between sub-paths. The cursor
   inside a real hatch failed the test → the click iterator moved on
   to the NEXT hatch in HashMap order and silently returned the wrong
   one. Rewrite the ray-cast to reset the previous-vertex / path-start
   state at every NaN, so each sub-path closes against its own first
   vertex and contributes its parity flip correctly.

2. Clicking on a hatch *inside* a block was either missing entirely
   (after the visible_hatches_for_click filter) or returning the
   block-defn source hatch handle (misleading — that handle isn't the
   thing the user sees). AutoCAD selects the parent Insert when a
   sub-entity of a block is clicked. Add `Scene::insert_hatches_for_click`
   which walks the same explode path `synced_hatch_models` uses and
   tags every exploded sub-hatch with its parent Insert handle, plus
   `hit_test::click_hit_insert_hatch` which iterates that list. The
   click resolver now tries wire → MSPACE hatch → insert-internal hatch
   in order, so clicking on a block-internal hatch selects the Insert.

Box / lasso select paths are unchanged — wire hit-test already picks
up Inserts, and dragging a box over block-internal hatches is rare
enough not to need its own resolution path yet.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/app/update.rs

@@ -1998,7 +1998,7 @@ impl H7CAD {
                                     a,
                                     p,
                                     crossing,
-                                    &self.tabs[i].scene.hatches,
+                                    &self.tabs[i].scene.visible_hatches_for_click(),
                                     vp_mat,
                                     bounds,
                                 ));
@@ -2031,7 +2031,7 @@ impl H7CAD {
                             handles.extend(scene::hit_test::poly_hit_hatch(
                                 &poly_pts,
                                 crossing,
-                                &self.tabs[i].scene.hatches,
+                                &self.tabs[i].scene.visible_hatches_for_click(),
                                 vp_mat,
                                 bounds,
                             ));
@@ -2058,7 +2058,17 @@ impl H7CAD {
                                 .or_else(|| {
                                     scene::hit_test::click_hit_hatch(
                                         p,
-                                        &self.tabs[i].scene.hatches,
+                                        &self.tabs[i].scene.visible_hatches_for_click(),
+                                        vp_mat,
+                                        bounds,
+                                    )
+                                })
+                                .or_else(|| {
+                                    // Block-internal hatch: resolve to the
+                                    // parent Insert (AutoCAD behaviour).
+                                    scene::hit_test::click_hit_insert_hatch(
+                                        p,
+                                        &self.tabs[i].scene.insert_hatches_for_click(),
                                         vp_mat,
                                         bounds,
                                     )
@@ -2096,7 +2106,7 @@ impl H7CAD {
                                 a,
                                 p,
                                 crossing,
-                                &self.tabs[i].scene.hatches,
+                                &self.tabs[i].scene.visible_hatches_for_click(),
                                 vp_mat,
                                 bounds,
                             ));