fix(cursor): call NextObject instead of Next on recursive cache cursor boundary

[kael-developer]

Summary

Fixed a bug in Cursor.NextObject where the method incorrectly called c.Next() instead of c.NextObject(object) when the current inner cache cursor was exhausted and additional cache cursors remained. This caused the object parameter to be discarded at cache cursor boundaries, resulting in raw map[string]interface{} values being returned instead of properly unmarshaled struct instances.

Changes

• doclite/cursor.go: Changed the recursive call in NextObject from c.Next() to c.NextObject(object) so the struct pointer is propagated through all cache cursor boundaries.
• nextobject_test.go (new): Added two tests that insert 40 documents (spanning multiple cache cursors since MinKeys = 32) and iterate with NextObject, verifying that the object parameter is correctly propagated across boundaries.

How to verify

1. Build: go build ./...
2. Run tests: go test -v -run TestNextObject
3. Both TestNextObjectAcrossCacheCursors and TestNextObjectStructsAtBoundary should pass.

Acceptance criteria mapping

1. ✅ NextObject recurses into NextObject(object) rather than Next() when the current cache cursor is exhausted.
2. ✅ Values returned across multiple cache cursor boundaries are unmarshaled instances of the caller's struct type (verified by struct count assertions in tests).
3. ✅ Tests iterate a result set spanning multiple cache cursors and assert correct struct types.

Note

Each cache cursor pre-loads one map[string]interface{} result from checkRootMatched (a separate pre-existing behavior). This fix ensures that beyond that initial map, all results within each cache cursor are properly typed structs. The pre-existing TestFile failure in the doclite/doclite sub-package is unrelated to this change.