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/semantic_review/message_kind_tests.rs

@@ -14,6 +14,7 @@ fn fixture(oa_kind: MessageKind, sa_kind: MessageKind) -> (Project, Id, Id, Id)
             .unwrap();
         *p.elements.get_mut(&id).unwrap().shared_mut().unwrap() = SharedBody::Occurrence {
             body: OccurrenceBody::Exchange {
+                operation: None,
                 exchange: None,
                 sender: None,
                 receiver: None,
@@ -358,6 +359,7 @@ fn message_group_reply_and_reference_take_require_explicit_call_mapping_both_dir
                 .unwrap();
             *p.elements.get_mut(&call).unwrap().shared_mut().unwrap() = SharedBody::Occurrence {
                 body: OccurrenceBody::Exchange {
+                    operation: None,
                     exchange: None,
                     sender: None,
                     receiver: None,