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/ui/overlay.rs

@@ -597,6 +597,7 @@ impl canvas::Program<Message> for SelectionCanvas {
                     b.line_to(Point::new(sp.x - h, sp.y + h));
                     b.close();
                 }),
+                GripShape::Circle => canvas::Path::circle(Point::new(sp.x, sp.y), h),
             };
 
             if grip.is_hot {