ui.at picks an origin plane where a click selects it (#575)

ui.at {plane} now returns the middle of the origin plane's square, or else the middle of a quarter that a click actually picks, so scripted clicks on XY no longer start a sketch on XZ from iso-like views.

crates/ui-egui/src/control.rs

@@ -357,7 +357,7 @@ pub fn handle(app: &mut SolveApp, ctx: &egui::Context, req: &ControlRequest) ->
                     .and_then(|id| st.sketch(id))
                     .map(|ss| ss.plane.to_world(solidcraft_engine::geom::Vec2::new(num(s, 0), num(s, 1))))
             } else if let Some(n) = p.get("plane").and_then(Value::as_str) {
-                crate::viewport::origin_planes(app).into_iter().find(|(name, _, _)| *name == n).map(|(_, _, q)| (q[0] + q[1] + q[2] + q[3]) / 4.0)
+                crate::viewport::origin_plane_target(app, &proj, n)
             } else if let Some(n) = p.get("axis").and_then(Value::as_str) {
                 // Along an origin axis, on its solid part.
                 let size = crate::selection::origin_size(app.cam.half_height());