* Fix symlink path traversal in skill archive extraction
`_safe_extractall` (the Python < 3.12 fallback used by `crewai skills`
archive unpacking) validated each member's *name* against the destination
but never validated symlink/hardlink *targets*. A malicious skill tarball
could plant a symlink escaping the destination (e.g. `link -> /home/user/.ssh`)
followed by a regular member written through it (`link/authorized_keys`),
escaping `dest` even though every member name resolves inside it — the
classic symlink-extraction traversal.
The 3.12+ path (`extractall(..., filter="data")`) already blocks this; the
fallback now mirrors it by rejecting absolute link targets and any link
target that resolves outside the destination directory.
Adds regression tests covering absolute and relative escaping symlinks plus
benign in-tree symlinks and ordinary archives.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
* Harden skill cache archive extraction
* Reject special skill archive members
---------
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Moves the registry/cache pieces of PR #5867 under crewai.experimental.skills
and the CLI commands under `crewai experimental skill`. The stable local-file
skills feature (loader, parser, validation, models) stays in crewai.skills.
Both entry points now require CREWAI_EXPERIMENTAL=1:
- resolve_registry_ref() calls require_experimental_skills() before resolving
- The `crewai experimental` CLI group raises UsageError when the flag is unset
SkillDownloadStarted/CompletedEvent move out of crewai.events.types.skill_events
into crewai.experimental.skills.events.
* refactor(skills): move 'version' off SkillFrontmatter into metadata
The skill version is now stored as `metadata.version` rather than a
top-level field on `SkillFrontmatter`. A `before` validator lifts any
top-level YAML `version:` into `metadata['version']` so existing SKILL.md
files keep parsing.
