* fix(web): refuse an existing script-export destination as invalid input
export_web_scripts refused an existing output directory or link correctly,
but reported it as artifact_operation_failed / execution_failure with no
field issue or recovery. SafeOutputTree.create raises that refusal as a
path failure before any output tree exists, and the export mapper wrapped
it as an artifact failure.
Attribute pre-admission path refusals to output_directory as an
AnalysisInputError, as environment export already does for its directory.
Both now share one helper owned beside SafeOutputTree; failures after the
tree is admitted keep their artifact semantics.
Fixes#6029
* fix(artifacts): type SafeOutputTree destination refusals
Admission conversion treated any cleanup-free path failure raised before
admission as a refusal of the selected directory, so an acquired-tree setup
failure, such as being unable to restrict a created root to 0700, blamed
valid output_directory or directory input.
SafeOutputTree.create now raises SafeOutputTreeDestinationRefusal for the
refusals of the selection itself: a relative or reserved root, an existing
root, and an accepted existing root that is not an empty directory. The shared
conversion accepts only that type, directly or wrapped by
SafeOutputTreeCreationFailure, so script and environment export no longer
track admission separately.
morluto