add test: pipe-command

[jjlai5]

This PR adds additional unit tests to improve coverage of the pipeline feature in CODEX. Since pipelines are widely used, this PR ensures that various edge cases and formats are properly tested.

✅ New Test Scenarios Covered:
• Multiple pipelines in a single command
• Pipelines without spaces, e.g., cmd1|cmd2
• Mixed operators involving pipelines and logical operators (&&, ||, etc.)

These additions aim to increase confidence in the correctness and robustness of pipeline handling.

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