Build a chain with a code gate, then add routing

Keep the model steps thin and put every check in code. ask is the only place that talks to Claude Code; the gate is a pure function of the extraction and the source text, so it can be re-run without any model; the router only returns a label and a switch decides what happens. The decision that matters most is what the gate checks: each quote must appear in the entry it cites, not just anywhere in the file.