restore_skill() falls back to p.name.startswith(f"{skill_name}-") when no
archive directory matches the requested name exactly. That fallback is meant
to catch the timestamped duplicate archive_skill() writes on a name collision
(<skill>-YYYYMMDDHHMMSS), but the bare prefix also matches any unrelated
archived skill named <name>-something. So restoring "git" can pull an archived
"git-helpers" out of .archive/, rename it to "git", and report success: the
requested skill is not restored and the sibling is gone from the archive.
Constrain the fallback to the exact suffix archive_skill() produces, a 14 digit
timestamp. The exact-name match and the recursive nested-archive walk are
unchanged, so nested and timestamped restores still work; unrelated siblings no
longer match.
Fixes#47647
992b922389