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/forms.rs

@@ -14,6 +14,7 @@ use iced::{
 use oa_core::*;
 use serde_json::{Value, json};
 use std::collections::{BTreeMap, BTreeSet};
+mod context_fields;
 mod data_fields;
 mod port_fields;
 mod view_fields;
@@ -44,6 +45,23 @@ pub struct ReferenceBrowser {
     pub page: usize,
 }
 
+pub(crate) fn set_shape_value(record: &mut Value, path: &str, value: Value) -> Result<(), String> {
+    if let Some(target) = record.pointer_mut(path) {
+        *target = value;
+        return Ok(());
+    }
+    // Ordinary messages omit operation=None in source/JSON. Authoring that one
+    // optional field must not require changing the historic record encoding.
+    if let Some(parent) = path.strip_suffix("/operation")
+        && parent.ends_with("/Occurrence/body/Exchange")
+        && let Some(fields) = record.pointer_mut(parent).and_then(Value::as_object_mut)
+    {
+        fields.insert("operation".into(), value);
+        return Ok(());
+    }
+    Err("Property no longer exists.".into())
+}
+
 pub struct Draft {
     pub kind: RecordKind,
     pub original: Id,
@@ -323,9 +341,7 @@ impl Draft {
         } else {
             value
         };
-        *candidate
-            .pointer_mut(path)
-            .ok_or("Property no longer exists.")? = value;
+        set_shape_value(&mut candidate, path, value)?;
         self.value = candidate;
         self.rebuild();
         Ok(())
@@ -333,10 +349,7 @@ impl Draft {
     /// Replace a workflow-authorized subtree without parsing unrelated inputs,
     /// including an invalid value which this replacement deliberately removes.
     pub fn shape_scoped(&mut self, path: &str, value: Value) -> Result<(), String> {
-        *self
-            .value
-            .pointer_mut(path)
-            .ok_or("Property no longer exists.")? = value;
+        set_shape_value(&mut self.value, path, value)?;
         self.rebuild_retaining(|old| (!within(old, path)).then(|| old.to_owned()));
         Ok(())
     }
@@ -355,7 +368,8 @@ impl Draft {
             || path.ends_with("/Port/contract")
             || path.ends_with("/Occurrence/body")
             || path.ends_with("/Event/body")
-            || path.ends_with("/message_kind");
+            || path.ends_with("/message_kind")
+            || path.ends_with("/ContextualLink/purpose");
         if !constructor {
             return self.shape_scoped(path, proposed);
         }
@@ -1697,6 +1711,9 @@ pub fn scoped<'a>(
 ) -> View<'a, Message> {
     match draft.value.pointer(path) {
         Some(value) => property(draft, project, value, path, label, false),
+        None if path.ends_with("/Occurrence/body/Exchange/operation") => {
+            property(draft, project, &Value::Null, path, label, false)
+        }
         None => text("This property is not applicable to the current target.")
             .size(12)
             .into(),
@@ -1711,6 +1728,9 @@ fn property<'a>(
     label: &str,
     skip_variant: bool,
 ) -> View<'a, Message> {
+    if let Some(view) = context_fields::property(draft, project, value, path) {
+        return view;
+    }
     if let Some(view) = view_fields::property(draft, project, value, path) {
         return view;
     }
@@ -2419,6 +2439,7 @@ mod tests {
                         receiver: Some(receiver),
                         message_kind,
                         reply_to,
+                        operation: None,
                         values: vec![],
                     },
                 },