fix(mcp): fix three failing unit tests in annotation layer tools

- AnnotationList.filters_applied used list[AnnotationFilter] which only
  allows col="short_descr", but ModelListCore injects a col="layer_id"
  ColumnOperator that fails Pydantic validation, causing KeyError on
  layer_id in the JSON response. Changed to list[ColumnOperator].
- test_get_annotation_layer_info_found: ModelGetInfoCore._find_object
  calls find_by_id(id, query_options=None), not find_by_id(id); updated
  assertion to assert_called_once_with(5, query_options=None).