Harden PATH export with sanitization to prevent empty element attacks (#12381)

* Initial plan

* Plan: Harden PATH export command in AWF firewall agent

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

* Harden PATH export with sanitization to remove empty elements and leading/trailing colons

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

* Simplify PATH sanitization logic per code review feedback

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

* Refactor PATH sanitization to a bash script (sanitize_path.sh)

Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>

* Add changeset [skip-ci]

* Merge main and recompile workflows

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Mossaka <5447827+Mossaka@users.noreply.github.com>
Co-authored-by: Jiaxiao Zhou <duibao55328@gmail.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Author: 4 people