feat: add managed types, source classes and scoped native calls

crates/objects/src/changes.rs

@@ -0,0 +1,26 @@
+use crate::ObjectRef;
+
+/// A precise field change or a replacement of an object's native contents.
+/// Entries are notifications, never roots; a source can be dead when consumed.
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub enum ChangeKey {
+    Attribute(String),
+    Contents,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ObjectChange {
+    pub object: ObjectRef,
+    pub key: ChangeKey,
+    pub version: u64,
+}
+
+/// Coalesced changes since the previous drain. Overflow requires the consumer
+/// to rescan its dependencies, rather than silently missing notifications.
+#[derive(Debug, Default)]
+pub struct ChangeBatch {
+    pub changes: Vec<ObjectChange>,
+    pub rescan_required: bool,
+}
+
+pub(crate) const MAX_PENDING_CHANGES: usize = 4096;