EvidenceState enum

How COMPLETE one piece of gathered evidence is. Sealed by the enum and consumed with an exhaustive switch (house style), so a new state cannot skip a projection's sufficiency check.

The distinction is the whole point of the canonical profile: an empty successful lookup (complete) is a REAL result, where a clipped one (truncated), an unwired source (unavailable) and a crashed one (failed) are known NON-answers. A lens is handed the state, never a bare snippet, so it can never read "nobody looked" as "nothing is there".

Three of those states are the lens's CONTEXT; only one is a deterministic GAP (_isDeterministicEvidenceGap). failed overrides the lens's report with an InsufficientEvidenceReport and spends the one-round regather budget, because the gather promised a record and then crashed. unavailable does NOT: the optional source was simply never composed, so the lens narrates the limitation and its report stands, exactly as it did before the canonical profile existed. truncated does NOT either (bead pow-gcx9): the record was clipped at a bound the gather declares, which every mature surface exceeds; the lens narrates the clip, and only its own insufficient-evidence outcome can hold the round on it.