Issue
Title: Fix parent reference warning
Description
Issue #, if available:
Description of changes:
Improves the parent-directory reference check in the S3 download path so that compare keys with a leading slash (e.g. /../foo) are correctly flagged.
The compare key is now anchored against the destination directory root before os.path.normpath() is applied, preventing the leading slash from collapsing the .. segment away.
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Task
Modify the repository so that the issue described above is resolved. The repository is checked out at base commit bc427faf6cff. Edit files in place; the verifier captures your changes via git diff and scores them against an oracle patch using SWE-RL-style diff-similarity reward.