- check-fork-drift.sh: compares each submodule HEAD against upstream/master,
reports behind/ahead counts, exits 1 if any fork exceeds threshold
- upgrade-forks.sh: fetches latest upstream, saves RB commits, resets to
upstream, cherry-picks RB patches with conflict handling and backups
- build-preflight.sh: wired drift check into preflight (threshold=50,
suppressible via REDBEAR_SKIP_DRIFT_CHECK=1)
- bootloader submodule pointer updated to latest upstream rebase
