IV / two-stage-least-squares conformance fixture

Suite path: conformance/estimate/iv_2sls

Generated inline by crates/antecedent/tests/estimate_conformance.rs — no CSV, no pinned baseline install. Clean-room synthetic SCM, deterministic from a fixed ExecutionContext seed.

Comparison: |estimate.ate - true_effect| < tolerance (finite-sample Monte Carlo check; not a StableFloat bitwise/analytic comparison).

Expected summary

Top-level keys: estimator, generation, identifier, notes, reference, tolerance, true_effect (7 fields).