A `...` after a document is already closed (only comments or blank lines since
the last `...`) ends nothing: a repeated document-end marker is valid YAML, so
consume it as a no-op rather than rejecting the stream as an unsupported
multi-document case. A second documentEnd is not emitted, so no phantom null
document is composed, and real content after the marker stays an error.
Fixes suite case M7A3 (parse-level conformance 313 -> 315); adds focused tests.
Mihaela M
056095ca3d