Checkpoint source 7 workflows and in-progress diagram authoring redesign

Preserve current core, source, REST, desktop, recovery, documentation and validation work, including AGENTS.md and the development summary. This is a work-in-progress checkpoint: the new compact palette has outstanding compilation errors and native acceptance; earlier passing gates retain their documented scope.

crates/oa-desktop/src/app/checkpoints.rs

@@ -62,6 +62,7 @@ impl App {
             self.selected,
         )
         .and_then(|snapshot| snapshot.with_workflow(self.workflow.as_ref()))
+        .map(|snapshot| snapshot.with_architecture(self.architecture.as_ref()))
         {
             Ok(snapshot) => snapshot,
             Err(error) => {
@@ -186,11 +187,21 @@ impl App {
         } else {
             Page::Diagram
         };
-        self.status = if self.migration.is_some() {
-            "Recovered source 5 as source 6 in an unsaved local copy. Draft text is preserved; workflow previews were rebuilt and semantic impact approvals need review. Choose Save as to save it."
+        if let Some(saved) = restored.architecture {
+            self.active_diagram = Some(saved.diagram);
+            self.layer = self.project().diagrams[&saved.diagram].layer;
+            self.explorer_index = crate::explorer::Index::new(self.project(), self.layer);
+            self.page = Page::Diagram;
+            self.architecture = architecture_authoring::State::restore(self, saved).ok();
+        }
+        self.status = if let Some(report) = &self.migration {
+            format!(
+                "Recovered source {} as source {} in an unsaved local copy. Draft text is preserved; workflow previews were rebuilt and semantic impact approvals need review. Choose Save as to save it.",
+                report.from_schema, report.to_schema
+            )
         } else {
-            "Recovered an unsaved local copy. Choose Save as to save it; the original file and hosted model are unchanged."
-        }.into();
+            "Recovered an unsaved local copy. Choose Save as to save it; the original file and hosted model are unchanged.".into()
+        };
         self.request_lint()
     }
 }