Backpropagate Specs

Use when implementation facts changed specs/docs.

Workflow

1. Generate grounded prompt: python3 bin/loop-factory backprop --agent codex
2. Read generated prompt under factory/prompts/backprop.codex.md.
3. Inspect git diff directly if needed.
4. Update only stale facts in specs/docs.
5. Add TODO/open question when implementation exposed missing decision.
6. Run relevant checks if docs/spec tests exist.

Rules