refactor: make the script simpler and more reliable

[mdqst]

Description

tidied up the script a bit:

• grab version from lerna.json in a simpler way
• make it work better across platforms (sed --version instead of uname)
• added safe quotes around variables

no actual changes to how it works, just cleaner and less likely to break.

Type of change

• Chore (non-breaking change that addresses non-functional tasks, maintenance, or code quality improvements)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Draft PR (breaking/non-breaking change which needs more work for having a proper functionality [Mark this PR as ready to review only when completely ready])
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How has this been tested?

ran the script locally on Mac and Linux - versions extract correctly and nothing breaks.

Fixes/Resolves (Optional)

just refactoring.

Examples/Screenshots (Optional)

N/A

Checklist

• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

Additional Information (Optional)

this improves readability and cross-platform reliability, no functional changes.

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[mdqst]

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