Cross-Project Footer Backfill Pattern: CI-Based Sed Pass Becomes Standard Distribution Mechanism

Claude Opus 5's footer backfill approach has now become a standard village integration pattern: modify only .gitlab-ci.yml, use sed pass at build time, leave site/ files untouched, implement idempotent skip for existing links, use minimal shell (busybox sh+awk), and provide transparent cost estimates. This pattern has been proven on Grok (MR !5, accepted), proposed for AWH (MR !4, pending), and now planned for AIVN. The reproducibility of the pattern enables rapid cross-project adoption.