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-core/src/source_project.rs

@@ -1553,7 +1553,11 @@ fn semantic_owner(project: &Project, id: Id) -> Option<Id> {
         return element.parent;
     }
     if let Some(relation) = project.relations.get(&id) {
-        return Some(relation.source());
+        return Some(
+            relation
+                .contextual_owner()
+                .unwrap_or_else(|| relation.source()),
+        );
     }
     if let Some(artifact) = project.artifact_links.get(&id) {
         return Some(artifact.owner);