[mark-devkit] distfiles-sync command doesn't close all file descriptors

```
❌ [dev-java/ant-bin-1.10.13] https://dlcdn.apache.org/ant/binaries/apache-ant-1.10.13-bin.tar.gz - apache-ant-1.10.13-bin.tar.gz: error on create file workdir/download/apache-ant-1.10.13-bin.tar.gz: open workdir/download/apache-ant-1.10.13-bin.tar.gz: too many open files
❌ [dev-java/ant-bin-1.10.13] (macaroni-cdn-hash) https://distfiles.macaronios.org/distfiles/de/4a/c6/de4ac604629e39a86a306f0541adb3775596909ad92feb8b7de759b1b286417db24f557228737c8b902d6abf722d2ce5bb0c3baa3640cbeec3481e15ab1958c9 - apache-ant-1.10.13-bin.tar.gz: error on create file workdir/download/apache-ant-1.10.13-bin.tar.gz: open workdir/download/apache-ant-1.10.13-bin.tar.gz: too many open files
❌ [dev-java/ant-bin-1.10.13] (macaroni-cdn-hash) https://distfiles-flat.macaronios.org/de/4a/c6/de4ac604629e39a86a306f0541adb3775596909ad92feb8b7de759b1b286417db24f557228737c8b902d6abf722d2ce5bb0c3baa3640cbeec3481e15ab1958c9 - apache-ant-1.10.13-bin.tar.gz: error on create file workdir/download/apache-ant-1.10.13-bin.tar.gz: open workdir/download/apache-ant-1.10.13-bin.tar.gz: too many open files
❌ [dev-java/ant-bin-1.10.13] (macaroni-cdn-flat) https://distfiles-flat.macaronios.org/distfiles/apache-ant-1.10.13-bin.tar.gz - apache-ant-1.10.13-bin.tar.gz: error on create file workdir/download/apache-ant-1.10.13-bin.tar.gz: open workdir/download/apache-ant-1.10.13-bin.tar.gz: too many open files
❌ [dev-java/ant-bin-1.10.13] (macaroni-cdn-mark) https://distfiles.macaronios.org/mark-distfiles/distfiles/apache-ant-1.10.13-bin.tar.gz - apache-ant-1.10.13-bin.tar.gz: error on create file workdir/download/apache-ant-1.10.13-bin.tar.gz: open workdir/download/apache-ant-1.10.13-bin.tar.gz: too many open files
```

This is something to fix to manage download of numerous files.

Start by locating the mark-devkit distfiles-sync command and reproduce the reported failure while downloading numerous files. Trace how downloaded files are opened and closed, then verify that the command completes without “too many open files” errors when processing the listed distfile sources.

Written by the indexing model from the issue text.