split-commit-into-stack

Split one oversized commit or branch into a stack of independently reviewable Graphite (gt) PRs — deciding what genuinely separates, what is atomic and must stay whole, and proving each lower PR builds and passes without the ones above it. Use when asked to "split this PR", "this commit is too big", "break this into a stack", "can we separate this out", or when a diff bundles several concerns across different layers.