fix(plugin-stack-persistence): wrap save failures in StackSnapshotRecordSaveError (#733)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ENvironmentSet

.changeset/wrap-record-save-error.md

@@ -0,0 +1,5 @@
+---
+"@stackflow/plugin-stack-persistence": patch
+---
+
+Wrap storage save failures in `StackSnapshotRecordSaveError` before invoking `onRecordSaveError` or rethrowing, matching the declared handler signature and the load-path behavior.

extensions/plugin-stack-persistence/src/stackPersistencePlugin.ts

@@ -30,8 +30,10 @@ export function stackPersistencePlugin<Metadata>(
         snapshot,
         metadata
       }).catch(error => {
-        if (onRecordSaveError) return onRecordSaveError(error);
-        else throw error;
+        const saveError = new StackSnapshotRecordSaveError(error);
+
+        if (onRecordSaveError) return onRecordSaveError(saveError);
+        else throw saveError;
       });
     }