Unable to accept symlinks in `-source`

Observed on v2.13.0

```sh
s3deploy -try -bucket my-example -source my-symlink
```

Expected output: A successful dry run
Observed output:

```
s3deploy v2.13.0, commit b2cefc36380166cf81ed5601d096a181963205a1, built at 2026-01-17T12:12:37Z
This is a trial run, with no remote updates.

Total in 3.93 seconds
read /Users/hunter/Code/my-symlink: is a directory
```