fix: generated Word artifact publication fails without a tool result

Browser acceptance reproduced a generated and previewed Word document failing at wx_artifact_publish with valid filename, workspace path and OOXML MIME. The run terminates without a publish receipt. Investigate the artifact staging/runtime boundary using bounded error metadata, add a reproducing regression, and preserve authorization, validation and idempotency. Root cause is not yet established; successful generation is not successful publication.

Start at the wx_artifact_publish entry point and trace the artifact staging/runtime boundary implicated by the browser acceptance failure. Reproduce the generated, previewed Word publication case, add a regression with bounded error metadata, and verify that authorization, validation, idempotency, and a publish receipt remain intact.

Written by the indexing model from the issue text.