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/persistence.rs

@@ -139,6 +139,13 @@ pub fn decode_with_report_limited(
     }
     let decoded = if bytes.iter().find(|b| !b.is_ascii_whitespace()) == Some(&b'{') {
         let header: serde_json::Value = serde_json::from_slice(bytes)?;
+        if header
+            .get("schema_version")
+            .and_then(serde_json::Value::as_u64)
+            .is_some_and(|v| v <= 6)
+        {
+            reject_source7_fields(&header).map_err(FileError::Invalid)?;
+        }
         if header
             .get("schema_version")
             .and_then(serde_json::Value::as_u64)
@@ -182,13 +189,14 @@ pub fn decode_with_report_limited(
             Some(3) => v3::migrate(serde_json::from_slice(bytes)?, limits)?,
             Some(4) => v4::migrate(serde_json::from_slice(bytes)?, limits)?,
             Some(5) => migrate_v5(serde_json::from_slice(bytes)?, limits)?,
-            Some(6) => DecodeResult {
+            Some(6) => migrate_v6(serde_json::from_slice(bytes)?, limits)?,
+            Some(7) => DecodeResult {
                 project: serde_json::from_slice(bytes)?,
                 migration: None,
             },
             _ => {
                 return Err(FileError::Invalid(
-                    "Unsupported or missing schema_version; expected 1, 2, 3, 4, 5 or 6.".into(),
+                    "Unsupported or missing schema_version; expected 1, 2, 3, 4, 5, 6 or 7.".into(),
                 ));
             }
         }
@@ -357,6 +365,70 @@ pub(crate) fn migrate_v5(
     })
 }
 
+/// Reject explicit new fields before serde defaults can erase their presence.
+/// This is also applied to source's resolved structured values.
+pub(crate) fn reject_source7_fields(value: &serde_json::Value) -> Result<(), String> {
+    match value {
+        serde_json::Value::Object(fields) => {
+            if fields.contains_key("ContextualLink") {
+                return Err("ContextualLink requires schema/source 7.".into());
+            }
+            if fields.get("Relation").and_then(serde_json::Value::as_str) == Some("ContextualLink")
+            {
+                return Err("ContextualLink view selectors require schema/source 7.".into());
+            }
+            if fields.keys().any(|key| {
+                matches!(
+                    key.as_str(),
+                    "Operation"
+                        | "ContextOwner"
+                        | "ContextSource"
+                        | "ContextTarget"
+                        | "ContextPurpose"
+                )
+            }) {
+                return Err(
+                    "Operation/contextual-link semantic facets require schema/source 7.".into(),
+                );
+            }
+            if fields
+                .get("Exchange")
+                .and_then(serde_json::Value::as_object)
+                .is_some_and(|body| body.contains_key("operation"))
+            {
+                return Err(
+                    "Exchange.operation requires schema/source 7, including explicit null.".into(),
+                );
+            }
+            for nested in fields.values() {
+                reject_source7_fields(nested)?;
+            }
+        }
+        serde_json::Value::Array(values) => {
+            for nested in values {
+                reject_source7_fields(nested)?;
+            }
+        }
+        _ => {}
+    }
+    Ok(())
+}
+pub(crate) fn migrate_v6(
+    mut project: Project,
+    limits: crate::language::ParseLimits,
+) -> Result<DecodeResult, FileError> {
+    if project.schema_version != 6 {
+        return Err(FileError::Invalid("Expected schema_version 6.".into()));
+    }
+    reject_source7_fields(&serde_json::to_value(&project)?).map_err(FileError::Invalid)?;
+    limits.check_model(&project).map_err(FileError::Limit)?;
+    project.schema_version = SCHEMA_VERSION;
+    Ok(DecodeResult {
+        project,
+        migration: Some(MigrationReport::data_upgrade(6)),
+    })
+}
+
 pub(crate) fn migrate_v1_with_report_limited(
     old: v1::Project,
     limits: crate::language::ParseLimits,