Enhance audit documentation and address critical Ref property issues

- Updated the audit guide to clarify the workflow and prerequisites for conducting a production-grade sync feature audit.
- Introduced a new plan file detailing fixes for critical issues identified in the two-way sync audit, including missing instance maps and stale paths after renames.
- Enhanced `ServeSession.lua` to correctly pass the instance map in patch updates, ensuring accurate handling of unresolved Ref properties.
- Implemented various fixes in `change_processor.rs` and `rojo_ref.rs` to address critical bugs related to Ref path handling and instance renaming.
- Added tests to verify the correct behavior of Ref properties and ensure robustness against edge cases.

These changes improve the reliability of the synchronization system and enhance the clarity of the audit process.

plugin/src/ServeSession.lua

@@ -735,7 +735,18 @@ function ServeSession:__confirmAndApplyInitialPatch(catchUpPatch, serverInfo)
 						end
 					end
 					Log.info("[Pull] Update: {}", instancePath)
-					local update = encodePatchUpdate(instance, change.id, propertiesToSync, self.__instanceMap)
+					local update = encodePatchUpdate(
+						instance,
+						change.id,
+						propertiesToSync,
+						self.__instanceMap,
+						function(sourceInstance, propertyName, targetInstance)
+							-- Defer unresolved Refs for retry via ChangeBatcher.
+							-- After the pull patch is sent, the target may appear
+							-- in the InstanceMap via forward-sync reconciliation.
+							self.__changeBatcher:deferUnresolvedRef(sourceInstance, propertyName, targetInstance)
+						end
+					)
 					if update then
 						table.insert(pullPatch.updated, update)
 					end