Expand description
Per-language extractor contract.
Every supported language exposes a zero-sized Lang type implementing
LangExtractor. The trait carries no dispatch overhead — it is the
formal contract every extractor must satisfy.
assert_conformance::<Lang>(graph, anchor) validates that a graph
produced by an extractor respects the contract. Each extractor’s
#[cfg(test)] extract_default helper invokes it on every fixture.