Investigate failing CI actions

[BruinGrowly]

Fix CI workflows by ensuring package installation and improving file handling for find | xargs commands.

The ljpw_gate.yml workflow was failing because the harmonizer package was not installed, leading to import errors for check_harmony.py. Additionally, find | xargs commands in multiple workflows were updated to use null-delimited output (-print0 | xargs -0) to prevent issues with filenames containing spaces.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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