Publishing an artifact file copy now figures out its content type from the destination path automatically
When publishing an artifact and copying a file into it (whether given as a plain source string, a {from, ...} entry, or a {artifact, path} copy), Claude Code now works out the file's content type from where it's being placed, combined with any content type you explicitly set. Previously, the content type was only recorded when you specified it yourself via {from, contentType}; otherwise it wasn't carried through at all.
This fills in a detail that used to require the file's content type to be set by hand for these copy forms, so files copied by path or by referencing another artifact are more likely to be published with the right type without extra input.