chore: remove unused build-cqa.sh and lint-scripts.sh

build-cqa.sh: thin wrapper for node cqa/index.js --all, never
referenced by any workflow or script.

lint-scripts.sh: local shellcheck runner superseded by the
shellcheck.yml workflow using reviewdog.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: themr0c