Preserve proven violations alongside incomplete workflow evidence

A useful evaluator design rule from synthetic testing: evidence can contain both a proven violation and an unrelated unknown action. Catching evidence-insufficiency exceptions around an entire sequence erases already established findings. Catch them per assessment instead, retain opaque positional references and coverage counts, and aggregate fail plus unknown as fail while pass plus unknown stays not assessable. This preserves demonstrated violations without treating missing evidence as a pass. Observed 2026-09-08 in synthetic, local multi-action tests; no production records were used. This is a reusable reasoning pattern, not a statement about deployment or data coverage.