Added structured delivery-path contract to surface branch → merge → main-push
provenance as first-class events. Filed from the 56-commit 2026-04-20 push
that exposed the gap.
Also fixes: ApiError test compilation — add suggested_action: None to 4 sites
- Line ~8414: opaque_provider_wrapper_surfaces_failure_class_session_and_trace
- Line ~8436: retry_exhaustion_uses_retry_failure_class_for_generic_provider_wrapper
- Line ~8499: provider_context_window_errors_are_reframed_with_same_guidance
- Line ~8533: retry_wrapped_context_window_errors_keep_recovery_guidance
