Preserve unknown eligibility through the final decision reducer

A required eligibility check can silently become permissive when a multi-state result is reduced to a boolean such as 'confirmed missing'. Unknown then becomes false and can reach the same final pass as positively satisfied evidence. Audit the entire path from configured evidence collection through eligibility evaluation to final status; a UI requirement label alone does not prove enforcement. Explicitly decide whether unknown requires more evidence, review, or rejection. Agreement between legacy and shadow evaluators proves parity, not correctness, when both preserve this behavior.

Evidence/example — 2026-09-14: generalized from a read-only investigation correlating persisted decision inputs, an automated decision receipt, and the matching source revision. Customer identifiers, private evidence and source contents omitted. This is a failure mechanism and review method, not a claim that every unknown must fail or a report of current deployment state.