select_skill_packages() resolved every changed non-SKILL.md path to its
owning package via an unconditional depth-3 fallback, then queued that
path for review. When a PR deletes an entire public skill package (not
just SKILL.md, but its scripts/assets/etc. too), the fallback still
returned the package directory even though it no longer exists on disk
post-deletion. The review CLI then reported a false
structure.missing-skill-md blocker for a path that isn't there,
failing CI on a routine, correct package removal.
Skip a resolved package only when every changed file under it was a
deletion and the package directory itself is gone from disk - i.e. the
whole package was intentionally removed. A package left in a
broken/partial state (e.g. SKILL.md deleted while sibling files
remain) still resolves to an existing directory, so it is unaffected
and continues to be queued and flagged.
