chore: fix handling of multi-line COMMITS variable

[brawncode]

Please go through the following checklist

• The PR title and commit messages adhere to guidelines here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/CONTRIBUTING.md. In particular, ! is used if and only if at least one breaking change has been introduced.
• I have run the CI check script with source scripts/run_ci_checks.sh.
• I have run the clean commit check script with source scripts/check_commits.sh, and the commit history is certified to follow clean commit guidelines as described here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/COMMIT_GUIDELINES.md
• The latest changes from main have been incorporated into this PR by simple rebase if possible; if not, then conflicts are resolved appropriately.

Rationale for this change

The COMMITS variable stores multiple lines, but it's passed into <<<, which can lead to incorrect handling of multi-line input. This could cause issues when processing commit messages.

What changes are included in this PR?

• Replaced <<< "$COMMITS" with a while read loop using process substitution < <(...).
• Ensures each commit message is processed correctly, avoiding potential line break issues.

Are these changes tested?

Yes, tested with different commit histories to confirm correct behavior. Let me know if further validation is needed! 🚀