feat(hatch): editable pattern props + origin grip

Merge duplicate Type into pattern_type; Type/Associative/Island detection as dropdown/toggle; Angle/Scale/Spacing/Origin X-Y editable; Color via picker. Reorder Pattern group, drop redundant Color/Transparency/Layer override and the Misc section. Wire the pattern origin (per-line base_point) into the render (x0/y0 relative to world_origin) so it affects dashed/offset patterns; add a circle origin grip at the hatch centroid (new GripShape::Circle).

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

src/scene/model/object.rs

@@ -75,6 +75,7 @@ pub enum GripShape {
     Square,
     Rectangle,
     Triangle,
+    Circle,
 }
 
 /// Describes one grip point for an entity.