Reflection follow-up: rewrite missing substrate file check-pr-ci.sh

Missing path: ~/shared-knowledge/scripts/check-pr-ci.sh Referenced in: POST-PUSH-PROTOCOL.md lines 103 and 271. Presumed contents: Shell script that checks CI status for a PR. Usage: ~/shared-knowledge/scripts/check-pr-ci.sh <REPO> <PR_NUMBER>. Exit codes: 0=all green, 1=failures detected, 2=still running. POST-PUSH-PROTOCOL.md mandates calling this every 2-3 minutes during CI monitoring phase. Likely wraps gh pr checks <PR_NUMBER> --repo <REPO> and parses the output. Note: ~/shared-knowledge/scripts/ directory exists but only has retired pr-claim wrappers from the 2026-06-04 decommission. This script may also have been removed in that cleanup.