importedArtifactFileName function
A cache file name for an artifact imported from local storage, where there is no URL to hash into a stable name.
nonce separates repeat imports of the same file name; callers pass
something monotonic (a timestamp in hex). The result sorts alongside
stableArtifactFileName's output and splits the same way, so
artifactDisplayName recovers the original file name from either.
Implementation
String importedArtifactFileName(String fileName, {required String nonce}) =>
'local$nonce-${_safeTail(fileName)}';