Super tiny fix typo

[fzyzcjy]

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[WindowsXp-Beta]

Addressed review comments in 955c3581:

• Shell injection (Update README_zh.md #1, [rollout] feat: implement partial rollout feature on rollout engine side #2): Fixed — using shlex.quote() for directory paths in both du and find commands instead of manual single-quote wrapping.
• Bare dict nit (fix typos in example docs #3): dict[str, int] is already typed — the guideline prohibits untyped dict, not typed generics. No change needed.
• Fragile .get() chain (fix: remove duplicate lines in usage.md #4): This pattern is copied from monitor_stale_jobs.py (the established convention). No change needed.