Extra directories added to the skill path containment allowlist.
These do NOT add new skill discovery locations — skills are still only
discovered from the standard directories. They exist so that symlinks inside
standard skill directories can point to targets in these additional
locations without being rejected by the containment check
in load_skill_content.
Set via DEEPAGENTS_CLI_EXTRA_SKILLS_DIRS env var (colon-separated) or
[skills].extra_allowed_dirs in ~/.deepagents/config.toml.
