Seed one storage entry: mint the upload session, wait for
awaiting-upload, tar-stream req.sourcePath (file or directory) to the
ingest URL, then poll until completed. If the stream fails, the session
is cancelled best-effort before rethrowing. Spawns tar on the host.
StorageSeeder over the platform's upload-session flow: mint a session (POST …/storage/{name}/uploads), wait for
awaiting-upload, tar-stream the local file/directory to the session's ingest URL, then poll the session untilcompleted. Requirestaron PATH (same as the CLI).