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/language.rs

@@ -84,7 +84,20 @@ impl ParseLimits {
             .elements
             .values()
             .map(|e| e.steps().map_or(0, Vec::len))
-            .sum();
+            .sum::<usize>()
+            .saturating_add(
+                project
+                    .relations
+                    .values()
+                    .map(|r| match &r.body {
+                        RelationBody::ContextualLink { source, target, .. } => source
+                            .references
+                            .len()
+                            .saturating_add(target.references.len()),
+                        _ => 0,
+                    })
+                    .sum::<usize>(),
+            );
         self.check_counts(graph, records, steps)
     }
 }
@@ -343,6 +356,10 @@ fn reference_field(key: &str) -> bool {
             | "local"
             | "field"
             | "path"
+            | "references"
+            | "occurrence"
+            | "allocation"
+            | "work"
             | "supertype"
             | "sender"
             | "receiver"
@@ -1386,9 +1403,10 @@ impl Parser<'_> {
     fn unit(&mut self, entry: bool, includes_allowed: bool) -> Result<SourceUnit, Error> {
         let mut header = if entry {
             self.take("arcadia")?;
-            if !matches!(self.text(), "3" | "4" | "5" | "6") {
-                return Err(self
-                    .error("Unsupported schema version: expected 'arcadia 3;', 'arcadia 4;', 'arcadia 5;' or 'arcadia 6;'."));
+            if !matches!(self.text(), "3" | "4" | "5" | "6" | "7") {
+                return Err(
+                    self.error("Unsupported schema version: expected arcadia 3, 4, 5, 6 or 7.")
+                );
             }
             let schema_version = self.text().parse().expect("checked source version");
             self.cursor += 1;
@@ -1606,6 +1624,7 @@ pub(crate) fn resolve_declarations(
             };
             match d.kind {
                 DeclKind::Element(kind, layer) => {
+                    if project.schema_version < 7 { crate::persistence::reject_source7_fields(&Value::Object(fields.clone())).map_err(&conversion_error)?; }
                     if project.schema_version < 6 && !crate::persistence::pre6_element_kind(kind) {
                         return Err(conversion_error(std::format!("{kind:?} requires schema/source 6.")));
                     }
@@ -1683,6 +1702,7 @@ pub(crate) fn resolve_declarations(
                     );
                 }
                 DeclKind::Relation(kind) => {
+                    if project.schema_version < 7 && kind == RelationKind::ContextualLink { return Err(conversion_error("ContextualLink requires schema/source 7.".into())); }
                     if project.schema_version < 6 && !crate::persistence::pre6_relation_kind(kind) {
                         return Err(conversion_error(std::format!("{kind:?} requires schema/source 6.")));
                     }
@@ -1691,7 +1711,9 @@ pub(crate) fn resolve_declarations(
                     }
                     let description =
                         take_string(&mut fields, "description", "").map_err(&conversion_error)?;
-                    let required: &[&str] = if kind == RelationKind::FunctionalExchange {
+                    let required: &[&str] = if kind == RelationKind::ContextualLink {
+                        &["owner", "source", "target", "purpose"]
+                    } else if kind == RelationKind::FunctionalExchange {
                         &["source", "target", "source_port", "target_port"]
                     } else {
                         &["source", "target"]
@@ -1722,6 +1744,7 @@ pub(crate) fn resolve_declarations(
                     );
                 }
                 DeclKind::Diagram => {
+                    if project.schema_version < 7 { crate::persistence::reject_source7_fields(&Value::Object(fields.clone())).map_err(&conversion_error)?; }
                     if project.schema_version < 6 && fields.contains_key("view_options") {
                         return Err(conversion_error("Diagram.view_options requires schema/source 6, including an explicitly supplied default value.".into()));
                     }
@@ -1852,11 +1875,13 @@ pub(crate) fn resolve_declarations(
         }
         return Ok(migrated);
     }
-    if project.schema_version == 4 || project.schema_version == 5 {
+    if matches!(project.schema_version, 4..=6) {
         return (if project.schema_version == 4 {
             crate::persistence::v4::finish(project, limits)
-        } else {
+        } else if project.schema_version == 5 {
             crate::persistence::migrate_v5(project, limits)
+        } else {
+            crate::persistence::migrate_v6(project, limits)
         })
         .map_err(|error| {
             (