Bound Process payload sizes and capture rendered order feedback

Box the optional Process menu context and changed order command without changing identity or command semantics. Add opt-in actual WGPU readbacks to the split-event OA/SA reorder evaluator. Strict all-target lint, format and affected desktop paths pass; native acceptance follows.

crates/oa-desktop/src/model_menu.rs

@@ -18,7 +18,7 @@ pub struct Request {
     pub route_segment: Option<(usize, Position)>,
     pub creation_point: Option<Position>,
     pub canvas: Option<route_edit::Context>,
-    pub process: Option<crate::behavior::topology::Context>,
+    pub process: Option<Box<crate::behavior::topology::Context>>,
     pub source_file: Option<String>,
 }
 impl Request {
@@ -65,7 +65,8 @@ impl Opened {
                 .is_some_and(|c| Some(c) != current_canvas(app))
             || request
                 .process
-                .is_some_and(|c| Some(c) != app.topology_context())
+                .as_deref()
+                .is_some_and(|c| Some(*c) != app.topology_context())
         {
             return None;
         }
@@ -96,7 +97,8 @@ impl Opened {
             && self
                 .request
                 .process
-                .is_none_or(|c| Some(c) == app.topology_context())
+                .as_deref()
+                .is_none_or(|c| Some(*c) == app.topology_context())
             && self
                 .request
                 .source_file
@@ -181,7 +183,7 @@ pub fn trigger(app: &App) -> iced::Element<'_, Message> {
                 request.canvas = app.route_context();
             } else if app.page == Page::Behavior {
                 request.canvas = app.state_context();
-                request.process = app.topology_context();
+                request.process = app.topology_context().map(Box::new);
                 if let Some(target) = app.diagram_selection.as_ref().and_then(|s| s.primary()) {
                     request.selection_target = Some(Box::new(target.clone()));
                     request.placement = match target {
@@ -362,7 +364,7 @@ pub fn popup(app: &App) -> Option<Menu<Message>> {
                 });
             }
             entries.push(Entry::separator());
-            if let Some(context) = request.process {
+            if let Some(context) = request.process.as_deref().copied() {
                 let endpoint = match request.selection_target.as_deref() {
                     Some(Target::ProcessOccurrence(endpoint))
                         if !endpoint.references.is_empty() =>