fix: replace unsafe os.system calls with Python stdlib in build script

[hobostay]

Summary

• Replace os.system("rm -rf ...") and os.system("cp ...") calls in build_with_pyinstaller() with safer Python stdlib equivalents (shutil, os)

Problem

The build_with_pyinstaller() function uses os.system() to run shell commands like rm -rf, cp, and mkdir. This is problematic because:

1. Security: os.system() spawns a shell, introducing potential injection vectors
2. Cross-platform: rm and cp are Unix-only commands; they don't exist on Windows
3. Error handling: os.system() only returns an exit code — no proper exceptions on failure

Fix

Replaced all os.system() calls with:

• shutil.rmtree() instead of rm -rf
• shutil.copy() instead of cp
• shutil.copytree() instead of cp -r
• os.makedirs() instead of mkdir

Test plan

• Run build_with_pyinstaller() and verify the build output is identical
• Verify it works on both Unix and Windows

🤖 Generated with Claude Code

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